Seven Republican candidates ganged up on Mr. Obama, who remains popular but could be vulnerable in the 2012 race due to the staggering economy and high unemployment.

Republican presidential hopefuls assailed President Barack Obama’s handling of the economy in their first major debate of the campaign season on Monday night, seizing on an issue they hope will open a path to the White House.

The New Hampshire debate 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 Mr. Obama than one another.

Instead, the seven Republican candidates ganged up on Mr. Obama, who remains popular but could be vulnerable in the 2012 race due to the staggering economy and high unemployment.

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

U.S. Rep. Michele Bachmann of Minnesota, invited as an unannounced contender, used the occasion to announce she had filed papers earlier in the day to enter the race, becoming the first female candidate in the field.

An outspoken critic of Obama, Ms. Bachmann is popular with libertarian—leaning tea party activists and social conservatives which makes her a credible threat to other candidates courting core Republican voters.

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.

Recent polls show Mr. Romney to be the Republican in the best position to defeat Mr. Obama in November 2012, but it’s not clear that he can win over the party’s right wing and secure the nomination. The other contenders are vying to fill the role of the anti—Romney candidate in the nomination contest.

M. Romney faces the challenge of trying to win over conservatives who see him as too moderate, especially because of his state’s health care plan, which was the model for Mr. Obama’s health care overhaul that many conservatives loathe.

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

But former Minnesota Gov. Tim Pawlenty at first sidestepped a chance to repeat his recent criticism of the Massachusetts state health care law that Mr. Romney signed as governor. It includes a requirement for residents to purchase health care coverage, a forerunner of the “individual mandate” that conservatives consider unconstitutional in the new federal law.

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

Mr. 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 of the 1930s.

“When 14 million Americans are out of work we need a new president to end the Obama Depression,” said former House Speaker Newt Gingrich.

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

Mr. Pawlenty labelled Mr. Obama a “declinist” who views America “as one of equals around the world,” rather than a special nation.

“If Brazil can have five percent growth, if China can have five percent growth, then America can have five 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.

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

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

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

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

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

Mr. 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. Mr. Paul said the president must tell the generals what to do. He said if he were president he would begin withdrawing troops almost immediately. The libertarian—leaning Paul said the United States has no purpose fighting a war in Afghanistan.

Former Utah Gov. Jon Huntsman, who recently stepped down as Mr. Obama’s ambassador to China, did not participate in the event. He is expected to announce his candidacy within a few weeks.

Already, this race has had its share of surprises as the Republican field has been slow to settle.

Several likely candidates decided not to run - Mississippi Gov. Haley Barbour, Indiana Gov. Mitch Daniels and former Arkansas Gov. Mike Huckabee 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.

Mr. Gingrich was trying to revive his campaign after suffering the mass exodus of the entire top echelon of his staff last week, an unprecedented event that left his chances of winning the nomination in tatters.

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

More In: International | News