MANCHESTER, N.H. >> 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 who shared a stage 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.

Said Rep. Ron Paul of Texas, the seventh contender on the stage: “As long as we are running a program that deliberately weakens our currency, our jobs will go overseas. And that’s what’s happening.”

As front-runner of a sort, Romney could well have expected criticism from his rivals.

But Pawlenty, a few feet away on the debate stage, at first sidestepped a chance to repeat his recent criticism of Romney in connection with the Massachusetts health care law that Romney signed as governor. It includes a requirement for residents to purchase coverage, a forerunner of the “individual mandate” that conservatives loath in the new federal law.

“My using ‘Obamneycare’ was a reflection of the president’s comments,” Pawlenty said, referring to a word he coined in a Sunday interview.

Bachmann — newest to the race — drew one of the loudest rounds of applause from a partisan debate audience when she predicted that Obama would not win re-election. He is “a one-term president,” she declared.

Instead, the most conservative presidential field in memory all but said what Ronald Reagan once preached — that government was the problem.

Romney said the auto bailout was a mistake, and said more generally, “Instead of thinking in the federal budget what should we cut, we should ask ourselves the opposite question, ‘What should we keep?”‘

Santorum criticized the financial bailout that Presidents George W. Bush and Obama backed, and Bachmann said she had worked in closed-door meetings in Congress to defeat the legislation when it was originally passed.

Pawlenty said politicians had caused the housing price bubble that contributed to the recession, and Paul blamed the recession on the Federal Reserve.

“As long as we do what we’re doing in Washington it’s going to last another 10 years,” Paul said. “What we’re doing now is absolutely wrong,” he said of federal programs meant to support the housing industry.

Even when they differed, the White House hopefuls did so in muted terms.

Santorum said he wholeheartedly supported Wisconsin Rep. Paul Ryan’s proposal to turn Medicare into a program in which the government subsidizes beneficiaries who would seek coverage from private insurance companies. Under the current system, the government pays doctors and other health care providers directly.

Pawlenty said he would have a plan of his own that shared some features with Ryan’s but would differ on other points.

The program’s finances are perilous, and Republican calls for fundamental change are at the heart of a roiling debate in Congress that is expected to extend into the 2012 campaign for the White House and both houses of Congress.

Cain bluntly told one questioner he was unlikely ever to receive in benefits from the money he has paid in through payroll taxes during his working life.

Gingrich, who was attacked by fellow conservatives when he criticized Ryan’s proposal for being mandatory,  said, “When you’re dealing with something as big as Medicare … you better slow down. … If you can’t convince the American people it’s a good idea, maybe it’s not a good idea.”

Gingrich, Bachmann, Romney and Pawlenty all pledged to seek repeal of the health care law that Obama won from Congress earlier in his term. The others on stage hold the same position.

Romney and Paul both said the United States should withdraw U.S. troops from Afghanistan, but disagreed on a timetable.

Romney said that generals in Afghanistan should guide the pullout schedule of American troops based on conditions on the ground. He said the troops should come home as soon as possible under those conditions. Paul said the president must tell generals what to do. He said if he were president he would begin withdrawing troops almost immediately. He said the United States has no purpose fighting a war in Afghanistan.

Former Utah Gov. Jon Huntsman did not participate in the event. He is expected to announce his candidacy within a few weeks.