BRETWOOD, N.H. - Republican presidential candidates were swarming Thursday on New Hampshire, the small Northeastern state that offers the next harvest of nominating delegates in the party's bid to evict President Barack Obama from the White House.

Former Pennsylvania Sen. Rick Santorum was intent on bolstering his new status as the party's top conservative alternative to Mitt Romney, the former Massachusetts governor and favourite of the Republican establishment.

Santorum came within just eight votes out of 122,000 cast of defeating Romney in Tuesday's Iowa caucuses, the nation's first nominating test. New Hampshire holds its primary election next on Jan.10 and will be awash in campaigning and political advertising for the next five days.

Santorum is running as an unabashed social conservative and opponent of abortion and gay marriage. Those positions, backed by his openly religious world view, caught fire in Iowa, where he came roaring upward in the final days of the campaign from single-digit polling support to a virtual tie with the more moderate Romney.

New Hampshire voters, however, are more moderate as well, and it seemed unlikely that Santorum's message would find the same natural constituency as it did in Iowa. Polls had shown him running far behind Romney, the heavy favourite in New Hampshire -- where he has a summer home. Romney is well known to voters there from his days as governor in neighbouring Massachusetts.

Republicans have found themselves deeply at odds this election year over which candidate is best suited to challenge the vulnerable Obama in the November election. The party mainstream believes Romney, with his executive experience as governor and businessman, will best resonate with voters nationally who are distressed by the state of the U.S. economy under Obama.

The economic recovery from the 2007-2009 Great Recession has been slow, and unemployment remains unacceptably high three years after Obama took office. While polls show most Americans blame his predecessor, President George W. Bush, for the economic collapse, Obama now carries the full weight of the recovery.

Romney has not been able to raise his support beyond the 25 per cent level in national opinion polls. He won just under 25 per cent of the vote in Iowa.

Some Republicans see Romney as insufficiently conservative on abortion, health care and other issues, and that creates a natural opening for Santorum as other conservative candidates leave the race.

At a morning stop in Salem, New Hampshire, before heading to South Carolina to prepare for its Jan. 25 primary, Romney labeled Obama a "crony capitalist" and a "job killer."

Santorum also focused on Obama.

"I don't think most Americans believe the vision of America that Barack Obama is selling," he told an audience in Manchester, the state capital. "We have a president who doesn't understand us."

Former Utah Gov. Jon Huntsman, who skipped the Iowa caucuses, chose to hammer at Romney, casting him as a captive of Wall Street who won't bring about the change the nation needs. Huntsman offered himself as the underdog for New Hampshire voters to take "from the back of the pack."

Newt Gingrich, still reeling from a barrage of negative ads unleashed on him by a pro-Romney super political action committee in Iowa, bluntly dismissed Romney's efforts to cast himself as the most electable challenger to Obama.

"The fact is, Gov. Romney has a very limited appeal in a conservative party," the former speaker of the House of Representatives said, setting aside his pledge to run a positive campaign.

A pro-Gingrich super PAC sought to undercut Arizona Sen. John McCain's endorsement of Romney, posting online an ad the 2008 Republican presidential nominee ran against Romney when the two competed for the party's nomination.

"Mitt Romney's flip-flops truly are masterpieces," said the ad revived by Winning Our Future.

The Republican field narrowed a little Wednesday with congresswoman Michele Bachmann dropping out after a last-place showing in Iowa.

Santorum has significant hurdles to climb if he hopes to prove that he is not the latest in a series of challengers who briefly topped polls only to fade quickly -- like Bachmann, Texas Gov. Rick Perry and Gingrich. After hinting that he might drop out, Perry announced Wednesday he would stay in the race.

It will be difficult for Santorum to recreate his success in Iowa, where he had campaigned almost nonstop for months. Santorum has only a skeleton staff in other states and has very little money.

Romney is much better placed with campaign staff and financing, and his campaign raised more than $32 million during the first nine months of 2011, the most recent data available.