MYRTLE BEACH, S.C. – The Republican presidential contenders on Mondaycampaigned their way into the first of two debates before a pivotal weekend primary in South Carolina, with Mitt Romney savoring an endorsement fromthe latest campaign dropout and his pursuers struggling to emerge as the race’s principalconservative.

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 littlelikelihood of that happening,either in the TV commercials, mail and other advertising blanketing the state ahead of Saturday’s voteor, 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 Obamathis fall.

Romney has victories in the only two contests of thecampaign thus far, the Iowacaucuses and New Hampshireprimary earlier this month.Gingrich has conceded that theformer 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 asanother one scheduled for Thursday in Charleston.

Romney is the leader in thepublic opinion polls in South Carolina, though his rivals hope the state’s 9.9 percentunemployment rate and thepresence of large numbers of socially conservative evangelical voters will allow one of them to slip by him.

Huntsman was the secondcampaign dropout to endorse Romney, after formerMinnesota Gov. Tim Pawlenty. Minnesota Rep. MicheleBachmann, who quit after a last-place finish in Iowa, has not yet said which of theremaining contenders shesupports. Herman Cain, who left the race in December after facing allegations of sexual impropriety, has promised anendorsement soon.

Huntsman’s partingannouncement included areference to the differences he and Romney had. But he left the podium without respondingto questions about his remarklast week, in the run-up to theNew Hampshire primary, that Romney was unelectable and out of touch.

It was unclear why Romney did not attend theannouncement. He was intown for a later campaignappearance and then the debate.