MANCHESTER, N.H. (AP) - Republican White House hopefuls condemned President Barack Obama's handling of the economy from the opening moments of their first major debate of the campaign season Monday night, and pledged emphatically to repeal his historic year-old health care overhaul.

"When 14 million Americans are out of work we need a new president to end the Obama Depression," declared former House Speaker Newt Gingrich, the first among seven contenders on stage to criticize the president's economic policies.

Rep. Michele Bachmann of Minnesota, invited as an unannounced contender for the 2012 nomination, upstaged her rivals for a moment, using a nationwide television audience to announce she had filed papers earlier in the day to run - a disclosure in keeping with a feisty style she has employed in a bid to become a favorite of tea party voters.

Obama was hundreds of miles away on a day in which he blended a pledge to help companies create jobs in North Carolina with a series of campaign fundraisers in Florida. He won the two states in 2008, and both figure to be battlegrounds in 2012.

The New Hampshire event unfolded more than six months before the state hosts the first primary of the 2012 campaign, and the Republicans were plainly more interested in criticizing Obama than one another.

Former Massachusetts Gov. Mitt Romney, who first sought the nomination in 2008, was the nominal front-runner as the curtain rose on the debate. But the public opinion polls that made him so are notoriously unreliable at this point in the campaign, when relatively few voters have begun to familiarize themselves with their choices.

Already, this race has had its share of surprises.

Several likely candidates decided not to run - Mississippi Gov. Haley Barbour and Indiana Gov. Mitch Daniels among them - and at least one who ruled out a race is reconsidering. Texas Gov. Rick Perry has said he will decide after the state Legislature completes its current session, and former Alaska Gov. Sarah Palin's plans are still unknown.

Gingrich, quick off the mark in attacking Obama, suffered the mass exodus of the entire top echelon of his campaign last week, an unprecedented event that left his chances of winning the nomination in tatters.

All seven flashed their anti-abortion credentials, and were largely unified in opposition to same-sex marriage, which is legal in New Hampshire.

Several praised a proposed amendment to the U.S. Constitution that would define marriage as between one man and one woman, a position popular among conservative voters. Bachmann said she supported that, but she added that states have the right to write their own laws and said that if elected president, she would not step into state politics - a nod to tea partyers who cherish the Constitution's 10th Amendment.

Obama's rivals found little if anything to like in what the president has done since taking office in the midst of the worst economic recession since the Great Depression.

Former Sen. Rick Santorum accused Obama of pursuing "oppressive policies" that have shackled the economy.

Former Minnesota Gov. Tim Pawlenty labeled Obama a "declinist" who views America "as one of equals around the world," rather than a special nation.

"If Brazil can have 5 percent growth, if China can have 5 percent growth, then America can have 5 percent growth," he added, shrugging off criticism that his own economic projections were impossibly rosy.

Businessman Herman Cain, a political novice, called for eliminating the capital gains tax as a way to stimulate job creation.

Romney stressed his experience as a businessman over 25 years as evidence that he can lead the nation out of a lingering recession.