US election 2012: Republican New Hampshire primary debate.

Reuters - U.S. Republican front-runner Mitt Romney emerged on Sunday from back-to-back debates in New Hampshire a bit dinged but not seriously dented as rivals stepped up attacks to slow his march toward the presidential nomination.

Two days before voters in the small New England state head to the polls for the first 2012 primary election, Romney took heat on a number of topics: his record as governor of neighboring Massachusetts, the attack ads run by an outside group on his behalf and a suggestion he would wither in the face of attacks from Democratic President Barack Obama.

But there was little to suggest the former venture capitalist had suffered any setback in a pair debates Saturday night and Sunday in New Hampshire, where he is heavily favoured to win.

"Romney was dinged in the second debate, but not seriously wounded," said Larry Sabato, political analyst at the University of Virginia. "Basically, the candidates firmed up their own individual base but I don't think they took much away from Romney either in terms of Republicans or independents."

Slowing Romney's momentum has taken on new urgency in the face of polls showing he is also favoured in the South Carolina primary on January 21, despite being seen as less socially conservative as his competitors in the church-going southern state.

Romney's campaign has said that jobs and the domestic economy will be the focus of voters across the country this year, overshadowing other factors.

Although Romney's win in the Iowa caucuses on Tuesday was an eight-vote squeaker over Rick Santorum, backing it up with a win in New Hampshire would be a feat never achieved by a Republican candidate who is not an incumbent, adding to a sense of inevitability about his candidacy.

The online exchange InTrade, which takes bets on the outcomes of events such as elections, now shows Romney with an 83 percent chance of winning the Republican nomination to run against Obama in the fall.

ROMNEY PAINTED AS MODERATE

And yet, the race for second continued to hold the Republican field in suspense, with former Santorum, libertarian congressman Ron Paul, former U.S. House of Representatives Speaker Newt Gingrich, Texas Governor Rick Perry and former Utah Governor Jon Huntsman all vying for the spot.

Santorum, whose lacklustre campaign caught fire in Iowa and who has pinned hopes more on the next contest in South Carolina, came out punching at Romney, even though he endorsed Romney in his 2008 run for the party's nomination.

"If his record was so great as governor of Massachusetts, why didn't he run for re-election," said Santorum, a former U.S. senator from Pennsylvania. Romney launched his unsuccessful 2008 White House bid just weeks after leaving the Massachusetts statehouse after one term.

Criticism of Romney zeroed in on whether the former governor of a moderate New England state would be the strongest candidate to fly the conservative flag against Obama in the November election.

Gingrich, hurt by a spate of negative ads organized by former Romney staffers, said Romney would "have a very hard time getting elected" and had policy positions that are not sufficiently different from Obama.

"There's a huge difference between a Reagan conservative and somebody who comes out of the Massachusetts culture who essentially has a moderate record," Gingrich said during the NBC/Facebook debate in Concord, New Hampshire.

But Romney defended himself as "a solid conservative" who was in politics on a detour from his business career as a venture capitalist. Acting like a front-runner, he kept his focus more on Obama than on his Republican rivals.

"I happen to believe that if we want to replace a lifetime politician like Barack Obama ... we've got to choose someone who is not a lifetime politician, who has not spent his entire career in Washington."

Gingrich bristled at Romney's attempts to paint himself as a reluctant politician.

"Can we drop a little bit of the pious baloney?" he quipped. "You were running for president while you were governor."

SPEAKING TO CAROLINA

In the most tumultuous nominating process in the Republican camp in decades, it is hard to know what voters want - a flagbearer of conservative values or a serious challenge to a vulnerable incumbent trying to revive the sagging U.S. economy.

Santorum is running hard on his socially conservative credentials and used the spotlight again on Sunday to reinforce that message. He also emerged unscathed from an exchange about gay rights.

Santorum "has accepted the fact that he's going to lose New Hampshire, maybe badly. He spoke more to South Carolina than to New Hampshire," Sabato said.

Santorum has been riding a wave of popularity after a narrow second-place finish to Romney in the first Republican presidential nominating contest in Iowa last week.

Often in the news for negative comments about gays, Santorum managed to strike a conciliatory tone, saying "every person in America, gay or straight" should be treated with respect and that he would still love a gay son.

One of the biggest applause lines came from Jon Huntsman, who responded to a comment Romney had made about him in Saturday night's debate in Goffstown, New Hampshire.

Romney had slapped Huntsman for "implementing" Obama's agenda as U.S. ambassador to China, a post he held until April.

Addressing debate moderator David Gregory, Huntsman said: "This country is divided, David, because of attitudes like that. ... The American people are tired of partisan divisions."

"There are five candidates (with) a shot at getting double digits in New Hampshire and I think they all helped themselves today," said Fergus Cullen, former chairman of the New Hampshire Republican Party.