Issue salience is a fundamental component of party competition, yet we know little about when, where, or why parties’ issue emphases converge or diverge. I propose an original operationalization of issue salience divergence, the extent to which parties’ issue emphases differ from each other in an election, that generates values at the party-election and country-election levels. I leverage data from party manifestos to calculate scores for 2,308 party-election combinations of 381 unique parties in 426 elections across thirty European countries, the most comprehensive dataset to date. I find that issue salience divergence is generally low and has starkly decreased over time, but countries and parties differ substantially. As an initial step in understanding these differences, I propose and test initial expectations of how party and democracy age, electoral systems, and party type alter the incentives for divergent issue salience.
“As a matter of fact, the definition of the alternatives is the supreme instrument of power; the antagonists can rarely agree on what the issues are because power is involved in the definition…[T]he choice of conflicts allocates power” (Schattschneider, 1975, 66).
Introduction
Political parties construct the lines of political competition by emphasizing some issues and deemphasizing others (Neundorf and Adams, 2018; Rosenblum, 2008; Schattschneider, 1975). Salience theory and issue ownership suggest parties should emphasize different issues from other parties to raise the importance of ‘their’ issues (Budge et al., 1987; Petrocik, 1996). If parties are historically tied to a distinct set of issues (Egan, 2013; Klingemann et al., 1994; Seeberg, 2017), parties should emphasize those issues to increase their relevance in citizens’ voting decisions (Bélanger and Meguid, 2008). Empirical tests of this general expectation, which have only covered a small number of countries and elections, find that parties converge on a shared set of issues (Banda, 2015; Kaplan et al., 2006b; Sigelman and Buell, 2004). We know little, however, about how issue salience divergence varies across countries, parties, and time despite its foundational role in party competition. We also lack systematic explanations for variance in the degree of divergence.
In this paper, I operationalize issue salience divergence in a way that explicitly connects the dyadic, party, and country levels of analysis to map and explain issue salience divergence over 30 countries in Western and Eastern Europe from 1945 to 2021. This data set allows me to plot the trajectory of issue salience divergence across a total of 426 national elections. This dataset is the most comprehensive picture of issue salience divergence to date.
My operationalization connects the country-election level to the party-election level, including observations of 381 unique parties. This connection is crucial because election-level aggregates obscure internal heterogeneity. In an election with a moderate level of issue salience divergence at the aggregate level, two parties may have very similar issue salience profiles while a third diverges, emphasizing issues neglected by the other two. The same aggregate level of issue salience divergence could also emerge from a system in which all parties are moderately divergent. Opening up additional levels of analysis creates the possibility of identifying where issue salience divergence comes from in a party system as well as its party-level determinants.
Crucially, data on parties and countries over many elections allow me to consider the influence of political institutions and long-run factors, which are difficult to assess in single-country case studies. Previous work focuses on short-term strategic decisions (Ansolabehere and Iyengar, 1994; Dolezal et al., 2014; Sigelman and Buell, 2004). However, the limited temporal scope of this research makes it difficult to assess factors like electoral institutions and societal change, which tend to be constant across time or change gradually. My dataset’s temporal and geographic coverage opens new avenues of research into the role of systemic factors in conditioning party strategy.
Descriptive evidence identifies a systematic trend toward issue salience convergence over issue salience divergence in this sample, as anticipated by earlier research (Banda, 2013, 2015; Dolezal et al., 2014; Sigelman and Buell, 2004). Parties tend to distribute their attention similarly to their competition, even in an era of political realignment (Dalton, 2018). The same is true across time. Issue salience divergence has declined in most countries over time. However, these tendencies are not universal. Viewing country- and party-level values reveals that some countries and parties are more divergent than others and display different trends, with some better characterized by increasing divergence.
To explain this variation, I evaluate the role of electoral institutions and party types. Specifically, I find that parties in proportional electoral systems have more divergent issue agendas than those in majoritarian systems because proportional representation permits parties to enter parliament and government with narrower support bases. Mainstream and older parties are also more convergent than new and challenger parties. I take these results as indications that social fragmentation, the decline of the class and religious cleavages, and the transition to catch-all parties have diminished the degree of issue salience divergence in European party systems.
Variation and determinants of issue salience divergence
Salience theory and issue ownership
Salience Theory argues that issue emphasis is at the core of party competition (Robertson, 1976). It posits that parties are tied to a central bundle of issues that distinguish them from other parties (Klingemann et al., 1994). Therefore, parties should stick to ‘their’ issues and avoid issues favoring other parties in an attempt to structure political competition beneficially (Riker, 1996). The repeated emphasis of core issues, in turn, leads to the development of a clear brand in the minds of the public. As Klingemann, Hofferbert, and Budge wrote, “Parties are historical beings. They stand for something. Each party is expected to stand for something that separates it from the competition” (1994, 24). Salience Theory, therefore, expects a high degree of issue salience divergence.
This insight also informs our understanding of issue ownership’s implications for party strategy. Petrocik (1996) argues that voters have enduring associations between parties and issues. Therefore, a party should benefit when its owned issues are more salient among the public, but suffer when the opposition’s owned issues increase in importance or when they begin to lose ownership of a salient issue in an election (Blomqvist and Green-Pedersen, 2004; Seeberg, 2017; Seeberg and Nai, 2021). While scholars disagree on whether issue ownership originates from—or is best conceptualized as—competence or association (Walgrave et al., 2012, 2015), whether it is the product of governance or salience (Egan, 2013), and how to operationalize the concept (Walgrave et al., 2016), the underlying assumption of a strategic incentive to emphasize owned issues persists across the literature.
However, empirical investigations of party issue allocation typically disconfirm this expectation. Party agendas tend to converge (Dolezal et al., 2014; Kaplan et al., 2006a; Sigelman and Buell, 2004), though this has only been investigated in a few countries and time periods. Parties do not seem to avoid issues emphasized by their opponents, particularly as campaigns come to a close (Seeberg, 2020a). Avoiding the primary issues of an opponent may signal aloofness or disconnection with the electorate. Engaging with an issue may, furthermore, represent an attempt to reframe a disadvantageous issue or defend past government action in that area (Banda, 2013, 2015). A party may even be trying to attack another party’s issue ownership of a salient topic (Seeberg, 2020b; Seeberg and Nai, 2021). In line with these empirical results, I expect that issue salience divergence is generally low across European cases.
H1:
In general, parties’ issue salience is more convergent than divergent.
The decline of traditional cleavages
While issue salience divergence may be lower than Salience Theory would suggest, that does not mean it always has been. The logic undergirding Salience Theory rests on the connection between political parties and clearly defined groups in society. For much of the 20th century, parties were rooted in cultural milieus, particularly in connection with the major social and political divisions of the day, namely the class and religious cleavages (Lipset and Rokkan, 1967). These linkages anchored parties in place, mobilized voters, and tethered the public to their political representatives with enduring bonds (Bartolini, 2000; Bartolini and Mair, 1990).
Today, however, these cleavages have largely lost their hold (Marks et al., 2022). The social bases of social democratic and Christian democratic parties have become more heterogenous and the predictive power of class and religion has declined (Gomez, 2022; Oesch and Rennwald, 2018). Cross-cutting the traditional cleavages, social divisions based on education, cosmopolitanism, and globalized economic competition increasingly structure party competition and voter decision-making (Dancygier and Walter, 2015; De Vries, 2018; Hooghe and Marks, 2018; Kuhn, 2011).
The decline of traditional cleavages coincided with changes in party structure (Katz and Mair, 1995; Kirchheimer, 1966; Mair, 2013). Mass parties, characterized by the mobilization of a homogenous base of support grounded in large social milieus should emphasize the issues that matter to their supporters. With the decline of traditional cleavages, parties sought to capture a more diverse set of voters from different elements of society. These catch-all parties become more leadership-controlled and office-seeking (Mair, 2013; Strom, 1990). I expect such a party to water down its emphasis on the core issues of its traditional base. Some parties may have even detached from society and instead collude with other parties and the state to maintain their position (Katz and Mair, 1995). Because this paper focuses on parties in general rather than specific party families, I proxy the decline of these cleavages with parties’ and democracies’ ages.
H2:
Issue salience divergence declines as parties and democracies age.
Electoral systems
Political parties operate within electoral systems that modulate the incentives for direct engagement with opposing parties. In electoral systems that require parties to win pluralities or majorities to take office, parties cannot focus on the priorities of a relatively small voter base. They must cultivate a broad set of supporters. Because majoritarian electoral systems trend toward having two major parties (Duverger, 1954; Singer, 2012), these parties have stark government-opposition relations in which the opposition has little choice but to engage with and criticize government policy (Lijphart, 2012).
Under proportional representation, parties do not need more votes than their opponents to get into parliament or even government. Although there are still benefits to capturing the median voter (Ezrow, 2008), parties in these systems tailor their appeals to a more cohesive set of supporters, with weaker incentives to directly address the issue emphasized by other parties. Therefore, I expect that issue salience divergence will be higher under proportional electoral systems than under majoritarian systems.
H3:
Issue salience divergence is higher under proportional electoral systems than under majoritarian electoral systems.
Mainstream versus non-mainstream parties
As I alluded to in the discussion of cleavage change, I expect issue salience divergence to vary between mainstream and non-mainstream parties. There are several ways the literature identifies mainstream parties. Spoon and Klüver (2019) draw the distinction based on ideology. Mainstream parties belong to the Christian democratic, conservative, social democratic, and liberal party families. They consider all other party families to be non-mainstream. Using similar language of dominant and challenger parties, De Vries and Hobolt (2020) distinguish between the two types based on government participation. Dominant parties are parties that have participated in government while challenger parties are those that have not.
In both cases, mainstream/dominant parties differ from non-mainstream/challenger parties in terms of their strategic priorities.1 Mainstream parties tend to prioritize office-seeking over policy-seeking. This means that they appeal broadly and incorporate a large number of issues into their appeals (Greene, 2016). Mainstream and dominant parties also have a history of serving in government, definitionally in the case of dominant parties. So, they have a reputation to protect and responsibility for policies that fall outside of their preferred issue areas (De Vries and Hobolt 2020). As a result, I argue mainstream parties’ issue emphases will have significant overlap.
Non-mainstream and challenger parties, however, focus on a core set of issues that they think is underemphasized in politics and look for wedge issues to split mainstream parties’ support bases (Van de Wardt et al., 2014). Their policy-focused appeal is predicated on diverging from the set of issues shared across mainstream parties. Challenger parties also lack governing experience. Therefore, they are able to maintain their focus on a divergent subset of issues with minimal pressure to defend a cabinet’s governing record.
H4:
Challenger/non-mainstream parties have higher levels of issue salience divergence than mainstream/dominant parties.
Data and methods
Measuring issue salience divergence
Issue salience divergence is the degree to which parties in a party system emphasize issues to different extents. Sigelman and Buell (2004) propose an index for the US case, but this results only in dyadic comparisons. This works well in a two-party system where both parties receive identical scores. In multi-party systems, scores for individual parties and party-systems as a whole are necessary to compare across cases and time periods. In this section, I walk through my operationalization that explicitly connects party-dyads to party-election and country-election level scores, followed by a concrete example for the generation of my measure in the UK’s 1979 election. Additional descriptive statistics for issue salience divergence beyond those discussed later in this paper can be found in Supplementary Appendix B.
I conceptualize issue salience divergence as a spectrum. At the convergent pole, parties issue emphases are identical. There is no distinction between parties in terms of how they allocate their attention across issues. At the divergent pole, parties’ issue emphases are not just different, but opposites. At the center of the spectrum is the midpoint where parties’ issue salience distributions are unrelated. Therefore, I argue that a correlation-based operationalization matches the concept as it captures both the strength and direction of the relationship between party dyads. To do this, I need a data source for parties’ issue salience across relevant domains and a way to scale these correlations to the relevant level of analysis.
I measure issue salience using MARPOR Project data. This data source takes each quasi-sentence from party manifestos and categorizes them into mutually exclusive topics. These data provide a consistent procedure for measuring this manifestation of the party agenda across countries and elections. The data also represent an unmediated depiction of the parties’ issue emphases. While no data set is perfect (Gemenis, 2013), the MARPOR project’s geographic and temporal inclusiveness, as well as its focus on issue attention, makes it an ideal window into the issues that parties want to make important in elections.
While previous studies have also used manifestos as a data source (Dolezal et al., 2014; Sigelman and Buell, 2004: 658), results using manifesto data may not perfectly generalize to other data sources. As longer documents, election programs discuss a wide range of issues and are released prior to the actual campaign, thereby incentivizing parties to cover a broad range of issues. Other indicators of the political agenda—such as campaign advertisements (Banda, 2013, 2015; Lipsitz, 2013), press statements (Seeberg, 2020a), and candidate speeches (Sigelman and Buell, 2004)—are more dynamic and targeted representations of the political agenda and may, therefore, present more divergent issue emphases. Because the goal of this paper is to investigate the trends and determinants of issue salience divergence across a long period of time and many countries, I am unable to assess the degree to which the results would differ using another data source. There is evidence that parties’ issue attention in manifestos and press releases are closely related, but parties emphasize their owned issues more strongly in press releases than in manifestos (Tresch et al., 2018: 37–38). Therefore, I proceed with manifestos as one valid—though conservative—indicator parties’ issue agendas and issue salience divergence.
I begin by calculating ISDit, issue salience divergence for a single party i in election t, using the formula below. I first take the Manifesto Project’s coding scheme, which includes some directional categories such as ‘pro-welfare state’ along with non-directional categories like ‘peace’, and condense them into 15 policy domains (Volkens and Merz, 2018).2 Critically, this categorization scheme allows me to calculate parties’ positions and salience for each category. Combining the positive and negative categories removes the positional component of the data yielding the salience of each domain, which I measure as the percent of the manifesto in that area.
I then take the correlation between the salience of these issue domains for each party dyad in an election, which I denote as Ci,j,t where i refers to the party of interest and j refers to a different party in election t. Strong positive correlations in this context indicate that the dyad’s issue emphases are quite similar. Negative correlations indicate greater differentiation between the parties in terms of emphasis allocation. I then calculate ISDit by taking the average of the correlation for the dyads including the party of interest, weighted by the vote share of the other parties, vj,t,. This value is then multiplied by negative one, so higher values indicate divergence and lower values indicate convergence This operationalization also treats large parties as more influential, which is appropriate as these are the most important parties in the system. Weighting by party vote share, in this case, follows the same logic as in the calculation of the effective number of electoral parties or ideological polarization, both of which weight parties by size (Dalton, 2008; Laakso and Taagepera, 1979). To arrive at a party-system level measure, I take the average of these party-level values.
Concrete example: United Kingdom parliamentary election 1979
Figure 1 plots issue salience for the 15 issue categories used in this paper for each of the parties included in the MARPOR data from the 1979 election in the United Kingdom. First, I calculate the correlations between the issue saliences of each party dyad in the election. Because there were only three parties in this election, I calculate correlations for the Labour-Conservative, Labour-Liberal, and Liberal-Conservative dyads. The dashed identity line indicates where all points would fall if both parties in a dyad had identical issue salience distributions. When the party on the y-axis emphasizes an issue more than the party on the x-axis, the point ends up above the line. When the party on the x-axis emphasizes an issue more, it falls below the line.
Figure 1. Scatterplots of issue salience across 15 issues for each party included in the MARPOR Project for the UK in 1979. Points correspond to the salience of a given issue by the two parties indicated on the x and y axes. The dashed line is an identity line. If both parties emphasized all issues identically, all points would fall along this line. The title of each panel indicates the correlation coefficient between the issue saliences of the two parties.
As can be seen in Figure 1, the Labour-Conservative and Labour-Liberal correlations are around 0.5, which is more divergent than the global average, but this is not surprising given the acrimonious nature of the 1979 election. In the Labour-Conservative dyad for example, the Conservative party emphasizes the Role of the State (free vs controlled markets) much more than the Labour Party, which fits with Margaret Thatcher’s ideology. The Conservatives also emphasize unions more than Labour, which reflects the state of affairs following the Winter of Discontent and the public’s souring towards unions at that time. Labour puts more emphasis on the welfare state and environment than the Conservatives.
The Liberal-Conservative dyad is particularly interesting in this election. The Liberal Party was the only party to emphasize Civil Rights (including democracy and law and order). This reflects the party’s emphasis on electoral reform including the voting system, the relationship between parliament and government, citizen’s rights, and reduction in crime. For perhaps obvious reasons, the two major parties in the system have much less to say on these issues, particularly electoral and governmental reform. The Liberal Party also called for an “environmental perspective” across all areas of policy. The differences between these priorities and those of the Conservative party are stark, leading to a low correlation of 0.097.
With these correlations, calculating issue salience divergence for a party in this election is the average of the correlations for each dyad including it. This average is weighted by the vote share of the other party in those dyads. I then multiply that average by −1, so higher values indicate more divergent issue emphases. This is just convention. The averages could be left as they are and be treated as issue salience convergence rather than divergence. I choose to multiply by −1 so that higher values mean more differentiation as is the case with standard measures of polarization and fragmentation. In this example, the issue salience divergence of the Conservative Party comes to −0.400, the Liberal Party −0.303, and the Labour Party −0.522. As the dyadic values indicate, the Liberal Party is the most divergent party in this election, and the Labour Party is the least. A score for the election is the simple average of these values because the party-level scores are already weighted by vote share. Using this method, the UK’s 1979 election has an issue salience divergence of −0.409, which is substantially more divergent than either the second 1974 election (−0.771) or the following election in 1983 (−0.834).
Independent variables
I argue that issue salience divergence varies due to political institutions, the decline of cleavages, and mainstream versus challenger status. I operationalize electoral systems using the tripartite division of party systems into majoritarian, mixed, and proportional from the fourth version of the Democratic Electoral Systems dataset (Bormann and Golder’s, Forthcoming). The majoritarian systems include both plurality and absolute majority systems, which should incentivize direct issue engagement to achieve pluralities and majorities. The proportional and mixed cases, however, provide weaker incentives to court diverse voters via broad appeals and should result in more distinctive issue emphases.3
H2 above argues that issue salience divergence declines over time due to the weakening of cleavages and the transition to catch-all parties. To reflect this, I measure time at the party-level with the party’s age, the difference between the year of the first election that a party enters the data, and the current election. Although measuring party age in this way will be collinear with the year in across-time analyses, there is still variation within elections as some parties will be older than others. I also include squared and cubed values to allow for the possibility of non-linear effects.
Lastly, I use the Manifesto Project’s classification of political parties into party families. I then use Spoon and Klüver’s (2019) categorization of these parties as either mainstream or challenger parties, which considers Christian democrats, conservatives, liberals, and social democrats to be mainstream.4 All other party families are considered challengers. While this operationalization is time-invariant, it does distinguish challenger parties as those seeking to introduce or increase the salience of a specific set of issues on the political agenda. These parties are also more policy-seeking than office-seeking, so they will maintain their core set of issues despite competitive pressures to expand their appeals.
Controls
In addition to the independent variables of interest, I also include indicators for executive type (presidential vs. semi-presidential vs. parliamentary) and region (Western vs. Eastern Europe) to account for the possibility that post-communist trajectories have led to different degrees of issue salience divergence (Vachudova and Hooghe, 2009). I do not make explicit predictions for the effects of either of these variables. I also include the number of years since 1945 in models where it would not be perfectly colinear with party age or age of democracy.
I also include ideological polarization on economic and non-economic issues as well as the effective number of electoral parties (ENEP) as election-level variables (Laakso and Taagepera, 1979; Sartori, 2016). I control for party system factors to account for the possibility that issue salience divergence is a reflection of the number of parties and degree of positional disagreement in the system. Note that although correlations between issue salience divergence and polarization (economic and non-economic) are significant and positive, they are low in magnitude (0.197 and 0.104 respectively). The correlation between issue salience divergence and the effective number of parties is not statistically significant. These values suggest that they may share determinants but are not mere reflections of each other.
Following previous literature, I calculate the standard deviation of party positions on economic and non-economic issues weighted by party vote share (Gunderson, 2021; Hazan, 1997; Kim et al., 2010). I calculate the party positions using data from the Manifesto Project because it covers all the cases included in the analysis. See Table 1 in the Supplementary Appendix for the division of categories into economic and non-economic.
Modeling
The operationalization of issue salience divergence forms a panel data set where each observation is a party-election. In the 30 European countries from 1945 to 2021 included in this paper, I have a total of 381 unique parties in 426 national elections that enter my analysis. As shown in the descriptive statistics, party observations can be aggregated to the country-election level. Therefore, this dataset contains both rich temporal and substantial cross-unit variation. Given that my hypotheses laid out above refer to both differences of level and change as well as having implications at multiple levels of analysis (party-election vs country-election), I use several modeling strategies to capture the variation of interest.
At the country-election level, I utilize OLS estimate models with all cases pooled, country fixed effects, and first differenced. The pooled analysis will act as a baseline model with which to compare the other two. Its results blend temporal and cross-unit variation. The country-election fixed effect model controls for between-country variation, so its results speak to the extent that the independent variables are related to temporal variation in issue salience divergence. The first-difference model takes this one step further by narrowing the effect of the independent variables to only changes between adjacent elections. The extent that the results from the fixed effect and first-difference models differ from the results in the pooled model indicates whether the pooled results refer primarily to differences across time or between countries.5
To better reflect the multilevel structure of the party-level models, I use multilevel models with random intercepts by party and country. This allows me to include variables referring to the parties themselves and contextual variables that may influence party behavior. The inter-class correlation coefficients indicate that both random intercepts warrant inclusion in the model and explain a substantial proportion of the overall variation. I also leverage the higher number of cases at the party level to test the robustness of results from the overall sample by running separate regressions for cases in Western and Eastern Europe. This split sample analysis clarifies the extent to which parties from either region drives the aggregate results.
Results
Descriptive evidence
Figure 2 presents histograms of the party-election level values (Panel A) and country-election level values (Panel B) of issue salience divergence for 30 West and East European countries (listed in Figure 3). Country-election values are the average of the party-election values in each election, given that the party-election values are already weighted by vote share. The observed range of values is smaller than the possible range in both panels. Issue salience divergence is based on correlation coefficients, so the theoretical range of the value goes from 1 (complete divergence) to −1 (complete convergence). Observed values overwhelmingly fall below 0, and the party-election distribution, in particular, skews toward very low values with a mean of −0.529 and median of −0.561. The country-level values are more normally distributed, but the clear trend is still toward convergence.6 The restricted variation present in this sample suggests that the behavior expected by Salience Theory—avoiding the opposition’s strengths to emphasize one’s own—is either absent or restricted to a few issues. The clear weight of the distribution leans towards convergence, and few cases have a value around 0, which would indicate a lack of meaningful correlation with other parties. I take this result as evidence in favor of H1. Parties’ issue saliences are more convergent than divergent on average.
Figure 2. Distribution of issue salience divergence at the party-election level (Panel A) and the country-election level (Panel B). Author’s calculation using data from the MARPOR Project.
Figure 3. Box plots of parties’ issue salience divergence by country. The horizontal line in each block represents the median value for that country. Points indicate outliers, which are more than 1.5 times the interquartile range from the value at the 75th percentile. Countries are ordered by ascending median values. Author’s calculation using data from the MARPOR Project.
Figure 3 disaggregates the distribution of party-election values by country, plotting the variation using box plots. There are two key observations from this figure. First, there is substantial between-country variation. Ordering the countries from left to right by ascending median values shows that, even with large internal variation, countries differ in the extent of issue salience divergence. The median value in Montenegro, Denmark and Greece, for example, is higher than the 75th percentile value in many of the countries under consideration. Second, the within-country variation is quite high. Most countries have some cases very close to −1 (complete convergence) and some cases around or above zero. These observations militate against a universal narrative of issue convergence.
Figure 4 reinforces this conclusion by plotting country-election values across time. There are strong country differences both in terms of the average level of issue salience divergence (also evident in Figure 3) and within-country developments over time. Issue salience divergence declines in Belgium, France, Norway, and Luxembourg. In the Netherlands, Switzerland, and Greece, however, there is evidence for either stable or even increasing issue salience divergence in the past 20 years. The expected general trend towards convergence over time (H2) is present, but it is not universal. Although convergence may be typical, it is more typical in some places and at some times than others.
Figure 4. Issue salience divergence aggregated by country-election plotted across time with a loess curve to capture a smoothed trend. Data are presented for all elections used in this study from the MARPOR Project.
Issue salience divergence also differs between different types of parties. Figure 5 aggregates parties by family rather than by country, using the categorization scheme from the MARPOR Project. The general time trend indicates issue salience convergence across party families, which provides additional descriptive support for H1 and H2. Most party families’ issue emphases became less distinct over time, particularly in the late 20th and early 21st century. Issue salience divergence peaked among social democratic and conservative parties, for example, in the 30 years following the Second World War. Challenger parties, such as greens and ethnic parties, have higher levels of issue salience divergence when they emerge but converge over time. This observation provides initial support for H4 that mainstream parties will be less divergent than challengers. Figure 5 further emphasizes that, although issue salience divergence is typically low, that is not true for all party families or time periods. This reinforces the importance of analyzing results at the party-election level in addition to the country-election level.
Figure 5. Issue salience divergence aggregated by party family-year and displayed across time with a loess curve to capture a smoothed temporal trend. I calculate issue salience divergence and allocate parties to party families using data from the MARPOR Project.
Country-election results
Table 1 below displays the results from the OLS models at the country-election level. Model 1 contains all observations and all covariates. Models 2 and 3 isolate the within-country variation through the inclusion of country-level fixed effects and first-differencing the data respectively. Executive type, the electoral system, and region are excluded from these two models as they are either consistent across time or change infrequently. Election year is only included in Model 1 because it is perfectly colinear with the age of democracy in a fixed-effect and first-differenced setting. Model 3 has 30 fewer cases than Models 1 and 2 due to losing the first election per country from the differencing. The R2 and Adjusted R2 for Models 2 and 3 refer to the percent of the within-country variation explained, i.e., ignoring the amount of variation explained by the fixed effects.
Beginning with the variables present in Model 1, the results for the mixed and proportional electoral systems support H3, issue salience divergence is higher in proportional electoral systems. Because the dependent variable is rescaled to have a mean of zero and standard deviation of one, the coefficient on proportional electoral systems can be interpreted as country-elections operating under proportional systems are, on average, 35% of a standard deviation more divergent than country-elections operated under majoritarian electoral rules.
Across all three models, the age of a democracy has a significant, negative effect on issue salience divergence. I take this as evidence in support of H2. The maturation of democracies and the concomitant weakening of the class and religious cleavage, and growth of the catch-all party lead to declining issue salience divergence. This effect persists in the country-fixed effect and first-difference models, indicating that this trend is present across time, not just between countries.
Although I did not set expectations for the relationship between issue salience divergence and other characteristics of party systems, issue salience divergence has a robust, significant, and positive relationship with ideological polarization both on economic and non-economic issues, which is present across all three models. However, there is no apparent relationship with the effective number of electoral parties.
Party-election results
Table 2 presents the results from the party-election level multilevel models. As in Table 1, Model 1 in Table 2 pools all cases.7 Models 2 and 3, however, split the overall sample of parties between parties in Western and Eastern Europe, respectively. Splitting the sample by geographic region will help to detect ways in which party and party system characteristics may have heterogeneous effects. Issue salience divergence and all continuous predictors are rescaled to have a mean of zero and a standard deviation of one. The coefficients for continuous predictors can be interpreted as the marginal effect of a one standard deviation increase in the predictor on issue salience divergence denominated in standard deviations.
Beginning with the electoral systems, the results at the party-election level disagree with Table 1. Proportional and mixed electoral systems have coefficients in the correct direction, but only the coefficient on mixed electoral systems is significant in Model 1. In Eastern Europe, the direction of the coefficient flips and regains significance, though it should be noted that there are no pure majoritarian electoral systems in the East European sample. Therefore, the coefficient on proportional systems is the expected difference from mixed systems, not the proportional-majoritarian contrast that motivated H3.
Turning to temporal variation, there is compelling evidence for the decay of issue salience divergence over time, as I predict in H2. The coefficient on years since 1945 is significant and negative in all three models. Party age is signed in the expected direction in Model 1, but fails to reach significance (0.1 level in Model 1). The Eastern European results contradict the pooled results once again. Party age has a positive, insignificant coefficient with a significant, negative coefficient on the square of age.
As the descriptive evidence above suggested, there is also a significant difference between mainstream and challenger parties, which persists across regions. In the full sample, mainstream parties’ issue divergence is just below 30% of a standard deviation less than challenger parties, thereby supporting H4. However, the difference between mainstream and challenger parties is over twice as large in Eastern Europe as in Western Europe, though the difference is significant in both regions. This variation would be obscured by an analysis on the country-election level.
Finally, the significant, positive relationship between polarization (both economic and non-economic) and issue salience divergence identified at the country-election level is also present at the party-election level. Ideological polarization on non-economic issues has similar effects across both Western and Eastern Europe while polarization on economic issues seems to only have a discernible effect in the West. The effective number of electoral parties remains less consequential. It reaches significance in Model 2, but the magnitude of the effect is smaller than either of the polarization variables. While I would not interpret these results as causal because party system factors likely share determinants, the significance of other predictors while controlling for these party systems factors suggests that issue salience divergence is not solely determined by other party system characteristics
Conclusion
This paper maps and explains issue salience divergences’ geographic and temporal variation in 30 European countries. In line with previous scholarship, parties’ issue emphases tend to be more convergent than divergent, and issue salience divergence declines as parties and democracies age. However, not all countries or parties follow the same trajectory. Some, like Belgium, Finland, France, and Norway register noted declines across time while Denmark, Greece, the Netherlands, and Switzerland display mostly stable or even increasing divergence.
Electoral systems are one institutional factor structuring issue salience divergence. Because proportional representation allows parties to enter parliament and even government with a relatively small social base, parties have few incentives to directly engage with issues that benefit their opponents. Instead, they can more narrowly cater to their own electoral bases and other proximate groups. Therefore, proportional electoral systems exhibit higher levels of issue salience divergence at the country-election level. The effect of the electoral system varies slightly at the party-level and between regions.
Challenger parties are also likely to have more divergent issue emphases than mainstream parties. These challengers attempt to disrupt the political status quo, often previously neglected wedge issues. If this is the case and challenger parties build their brands by emphasizing a novel set of issues in comparison to the mainstream parties, then their issue salience divergence should be higher. Indeed, challenger parties’ issue salience divergence is around 30 percent of a standard deviation higher than mainstream parties, and this effect is even stronger in Eastern Europe.
The descriptive and multivariate findings presented in this paper also suggest promising avenues for future work. The disaggregated party-election level results indicate that the correlates of issue salience divergence in Eastern Europe differ from West European party systems. The causes and consequences of these differences should be of academic and practical interest given recent trends in democratic backsliding in Eastern Europe. Additionally, the evidence presented here focuses on differences between countries and parties as well as aggregate trends over time. Further research should consider why some countries with similar electoral systems display such divergent over-time trends as well as more precisely capturing the process of cleavage decay and rebirth.
Acknowledgments
This article benefited from generous feedback from Gary Marks, Liesbet Hooghe, Evelyne Huber, John D. Stephens, Jim Adams, Devin Case-Ruchala, Amanda Aziz, Nicolás de la Cerda, Michael Greenberger, Ashley Anderson, participants of the Lessons of Postfunctionalism conference, and three anonymous reviewers.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
1. In practice, the two definitions categorize parties very similarly. Despite the dominant-challenger distinction allowing party status to very by time, a comparison of the two systems indicates 70% of party-elections end up in the mainstream-dominant or non-mainstream-challenger quadrants. I expect both definitions to operate similarly as it relates to the strategic behavior of parties’ issue emphases, so I use the terms mainstream and dominant parties interchangeably as well as the terms challenger and non-mainstream.
2. For a full breakdown of the allocation of MARPOR project codes to issue domains and the allocation of these domains to economic or non-economic, see Supplementary Appendix A. On average, the categories included cover 59% of parties’ manifestos, which is about 9 percentage points more than the categories included in the RILE index, as a benchmark. Table 2 in Supplementary Appendix A shows the differences in categories.
3. As a robustness check, I also use Gallagher’s disproportionality index as a continuous operationalization in Table 1 of Supplementary Appendix C as it allows me to include the variable in over-time analysis. Results using the continuous measure do not diverge from the categorical measure.
4. As a robustness check, I include a government membership-based operationalization of dominant versus challenger party status in Supplementary Appendix C, which comes to the same conclusions as the party-family based measure.
5. To account for the effect of autocorrelation and common shocks across cases, I present models with lagged dependent variables and prais-winsten regressions with AR1 autocorrelation in the appendix. The results under these alternative specifications do not diverge from those presented in the main manuscript.
6. These results are very similar to those from other country case studies in Austria and the US (Dolezal et al., 2014; Sigelman and Buell, 2004). Although different data sources and categorizations schemes make direct comparisons difficult, they all identify a clear trend towards more convergence than divergence. My approach differs in that explicitly allows for the scaling of the measure from the party-dyad to the country-election level of analysis.
7. Table 7 in Supplementary Appendix C reruns Model 1 while controlling for the percent of the manifesto covered by the Volkens and Merz’s (2018) categories. Adding this control variables does not substantively alter the results.
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Jacob R Gunderson is a PhD Candidate at the University of North Carolina at Chapel Hill. His research focuses on party competition, party brands, and inequality. His research has been published in the British Journal of Political Science, Policy and Society, and Political Behavior.
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Jacob R Gunderson, Department of Political Science, University of North Carolina at Chapel Hill, 361 Hamilton Hall, CB 3265, UNC Chapel Hill, NC 27599-3265, USA. Email: [email protected]
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