What is the link between changing economic and social circumstances and the rise of populism in Western Europe? And what does the rise of populism tell us about the political economy of mobilization at a time when party systems are changing before our eyes? A political economy approach to populism must be attentive to the long-term changes in politics and society that help to explain: what kinds of people are mobilized by what kinds of parties; the changing role of place in fostering political mobilization; the new networks of mobilization that underlie populist success; trajectories and pathways of mobilization; and the effects of the eclipse of class by risk, inequality, and austerity as mobilizing experiences.