01/16/2012 05:11 pm ET Updated Jan 16, 2012

Republican Debate Tonight: GOP Candidates Facing Off Ahead Of South Carolina Primary

MYRTLE BEACH, S.C. — The Republican presidential contenders on Monday campaigned their way into the first of two debates before a pivotal weekend primary in South Carolina, with Mitt Romney savoring an endorsement from the latest campaign dropout and his pursuers struggling to emerge as the race's principal conservative.

Hours before the debate, former Utah Gov. Jon Huntsman withdrew from the race and announced his support for Romney despite their differences. He appealed to all remaining contenders to stop attacking one another.

There appeared little likelihood of that happening, either in the TV commercials, mail and other advertising blanketing the state ahead of Saturday's vote or, possibly, on the debate stage itself.

Romney wasn't present for Huntsman's endorsement, and Newt Gingrich, Rick Santorum, Rick Perry and Ron Paul all but ignored it as they sought to slow the front-runner's momentum in the race to pick a Republican rival to President Barack Obama this fall.

Romney has victories in the only two contests of the campaign thus far, the Iowa caucuses and New Hampshire primary earlier this month. Gingrich has conceded that the former Massachusetts governor will likely be the party's nominee if he is similarly victorious in South Carolina, an assertion that none of the others in the race has so far contested.

That raised the significance of the night's debate, as well as another one scheduled for Thursday in Charleston.

HuffPost's Howard Fineman reports:

South Carolina is the home of anti-federal sentiment going back to the 1820s, and the birthplace of the modern, Southern-based GOP thanks to figures like Strom Thurmond, Roger Milliken and Lee Atwater.

The state is to modern Republicanism what Mecca is to Islam: a holy place of its founding history, feuds, orthodoxy and authority.

Before 1980, South Carolina had selected its delegates by convention, a suitably elitist and tightly-controlled situation for local Republicans. But seeking an early boost in what had become a Southern-based party, Reagan operatives and loyalists engineered the switch to a primary system. Reagan won in 1980 and was on his way to the White House.

A win now by Romney -- a Yankee, a relative moderate, an Ivy Leaguer and a Mormon -- would be the ratification he desperately needs from voters who, so far, still regard him with mere tolerance at best and deep antagonism and suspicion at worst.

To be sure, Romney can still slog on to the nomination if he loses South Carolina. The Florida primary, ten days later, is a mega-state event in which only he and Ron Paul have the in-house resources to compete.

But losing the Palmetto State, given its history and what is likely to be a big turnout, would reinforce a narrative Romney can ill-afford: that he's a likely nominee by default, resented and unloved.

Romney is the leader in the public opinion polls in South Carolina, although his rivals hope the state's high, 9.9 percent unemployment rate and the presence of large numbers of socially conservative evangelical voters will allow one of them to slip by him.

Huntsman was the second campaign dropout to endorse Romney, after former Minnesota Gov. Tom Pawlenty. Minnesota Rep. Michele Bachmann, who quit after a last-place finish in Iowa, has not yet said which of the remaining contenders she supports. Herman Cain, who left the race in December after facing allegations of sexual impropriety, has promised an endorsement soon.

Huntsman's parting announcement included a reference to the differences he and Romney had. But he left the podium without responding to questions about his remark last week, in the run-up to the New Hampshire primary, that Romney was unelectable and out of touch.

It was unclear why Romney did not attend the announcement. He was in town for a later campaign appearance and then the debate.

Gingrich and Perry both began their day at a Martin Luther King Jr. Day observance, where they praised the legacy of the slain civil right legacy.

At about the same time, Santorum was complaining that attacks launched against him by a political action committee supporting Romney was spreading lies. He called on Romney to ask the group to edit or remove its ads from the air.

The attack on Santorum is patterned after one that helped send Gingrich into a nosedive in the polls in the final weeks of the Iowa caucus campaign.

Gingrich made similar demands on Romney to rein in his supporters, but was ignored.

Paul, who generally keeps a light campaign schedule, had a mid-afternoon speech to the state tea party convention.