(CBS/AP) With the USS Yorktown as a backdrop, Sen. John Kerry of Massachusetts officially declared his candidacy for the Democratic presidential nomination on Tuesday, telling supporters that "George Bush's vision does not live up to the America" that Kerry defended as a decorated war hero.

Kerry, a Vietnam War veteran, presented himself as the alternative to the Republican leader — and the Democrat with the credentials to emerge from the crowded field of nine aspirants and seize the party's nomination.

"In challenging times we need leadership that knows how to make America safer, that knows how to put America back to work," Kerry told the crowd. "The president has misled America and he has made our path more difficult as a result."

The four-term senator made his formal announcement after months of campaign-style appearances and debates with fellow Democratic presidential hopefuls.

"I reject George Bush's radical new vision of a government that comforts the comfortable at the expense of ordinary Americans," Kerry said. "George Bush's vision does not live up to the America I enlisted in the Navy to defend."

John Forbes Kerry has the initials of a one-time Democratic president — JFK — and a comparable pedigree — Ivy League education, commander of a small Navy craft during wartime and Massachusetts senator. Perceived as the front-runner early on in this campaign, that notion evaporated in the heat of rival Howard Dean's summer surge.

While the bulk of his speech was aimed at President Bush, Kerry also took aim at his Democratic foes.

"Some in my party want to get rid of all tax cuts — including those for working families," he said. "That's wrong. We need to be on the side of America's middle class and I've proposed a tax cut for them because it's the right way to strengthen our economy."

Dean has used an aggressive anti-Washington theme to gain momentum, coupled with his staunch opposition to the U.S.-led war against Iraq. The former Vermont governor, who has called for repealing all of Mr. Bush's tax cuts, vaulted to a 21-point lead over Kerry in New Hampshire.

"Today, with confidence in the courage of our people to change what is wrong and do what is right, I come here to say why I'm a candidate for president of the United States," Kerry said.

Kerry was joined by crew members of a Navy gunboat he commanded in Vietnam, where he won a Silver Star, Bronze Star and three Purple Hearts. Introducing Kerry was former Sen. Max Cleland of Georgia, who lost both legs and an arm in Vietnam combat. It is all part of Kerry's core argument that his military experience gives him unique credibility among the Democratic contenders to confront Mr. Bush on national security issues.

Appearing on CBS' The Early Show on Tuesday, Kerry criticized President Bush's handling of the situation in Iraq and defended his own decision to vote in the Senate to support the president's call for military action against Saddam Hussein.

"I voted to do the responsible thing for America which was to have a threat of force to hold Saddam Hussein accountable and to go the United Nations," he said.

"But the right thing to do was also to build up a coalition with other countries, to show the diplomatic skill to build that coalition, to show the patience to build the legitimacy and consent of the world for what you are doing and not to rush to war; to do so with a plan for winning the peace. And I warned the president, last January. I said, 'Mr. President, do not rush to war, take the time to build the coalition, because it's not winning the war that's hard, it's winning the peace that's hard.'"

While Kerry has sought to focus attention on his war-hero background, some have urged him to broaden his appeal. With a distinctively martial theme for his announcement, there was little evidence he was taking that step.

"Americans have always had the extraordinary courage to do what's right for the country," said Kerry. "He (Bush) has turned it into a game for the privileged."

The choices Kerry faces with a campaign that's faltered early are hardly new.

Former Vice President Al Gore relocated his campaign to Nashville, Tenn., and pared back his staff when his campaign stumbled early in the 2000 presidential race.

After South Carolina, where Democrats vote during the third week of the nominating season, Kerry was headed to Iowa where precinct caucuses take place Jan. 19. On the second day of his announcement swing, Kerry was heading to New Hampshire, which has tentatively set its primary for Jan. 27, before heading home to Boston and a hometown rally.