CHARLESTON, S.C. — Jon M. Huntsman Jr. informed his advisers on Sunday that he intends to drop out of the Republican presidential race, ending his candidacy a week before he had hoped to revive his campaign in the South Carolina primary.
Mr. Huntsman, who had struggled to live up to the soaring expectations of his candidacy, made plans to make an announcement as early as Monday. He had been set to participate in an evening debate in Myrtle Beach.
Matt David, campaign manager to Mr. Huntsman, confirmed the decision in an interview Sunday evening. “The governor and his family, at this point in the race, decided it was time for Republicans to rally around a candidate who could beat Barack Obama and turn around the economy,” Mr. David said. “That candidate is Gov. Mitt Romney.”
A third-place finish in the New Hampshire primary last week failed to jump start his flagging candidacy, aides said, and his campaign limped into South Carolina with little money. Mr. Huntsman has spent days pondering his future in the race, but aides said that he concluded he was unlikely to topple Mitt Romney or match the momentum of his Republican rivals in the conservative Southern primary.
The decision from Mr. Huntsman came on the same day that he received the endorsement from The State, the newspaper in the capital of Columbia. He had campaigned in South Carolina over the weekend, not giving any indication that the end was near.
Mr. Huntsman first signaled his presidential ambitions here in South Carolina in May, days after returning from Beijing, where he had been the United States ambassador to China. He surrounded himself with a veteran roster of advisers who positioned Mr. Huntsman as a new brand of Republican.
He announced his candidacy in June, in the shadow of the Statue of Liberty, calling for a more civil kind of presidential campaign and promising a better future than the one that President Obama would provide.
“He and I have a difference of opinion on how to help a country we both love,” Mr. Huntsman said of Mr. Obama. “But the question each of us wants the voters to answer is who will be the better president, not who’s the better American.”
But the campaign of “civility, humanity and respect” that Mr. Huntsman promised quickly faded into the background as his Republican rivals seized the attention — and the support — of a party faithful that seemed more interested in red meat politics.
Voters also seemed wary of a candidacy by a man whose most recent service was to the very many he now wanted to oust. Fawning letters that Mr. Huntsman wrote about Mr. Obama’s leadership did not help that case.
For months, Mr. Huntsman languished near the bottom in the national polls and eventually gave up on competing in Iowa. He moved his campaign headquarters to Florida, betting that he could wait until that primary to make his move.
But as the first contests got closer, Mr. Huntsman made the decision to move his campaign to New Hampshire, where he hoped that the presence of independent voters would boost his chances.
Mr. Huntsman did better in New Hampshire than polls might have suggested, but he came in a distant third behind Mitt Romney and Ron Paul.
Mr. Huntsman’s campaign had been spearheaded from the beginning by John Weaver, a veteran Republican consultant who had once been a top adviser to Senator John McCain during his presidential bids.
Mr. Weaver had argued that Mr. Huntsman was just the person to take on Mr. Obama. The son of a billionaire corporate titan from Utah, Mr. Huntsman was the two-term governor of Utah with impeccable foreign policy credentials.
And Mr. Obama’s top advisers seemed to see the danger in Mr. Huntsman’s candidacy as well, signaling in 2009 that they thought he might a strong presidential contender.
At one point in January of 2011, Mr. Obama joked about a possible Huntsman candidacy at a news conference, saying that “I’m sure that him having worked so well with me will be a great asset in any Republican primary.”
The impact of Mr. Huntsman’s departure is not clear. Polls have indicated that he has little support in South Carolina and his lack of money means that he had been unable to affect a campaign conversation that is dominated by television commercials now that it has moved out of the first two early primary states.
But his decision to leave at the start of the week means that the two debates this week — one on Monday and another on Thursday — will be less crowded.
And his quick move to back Mr. Romney could help the front runner withstand efforts by social conservatives in South Carolina to coalesce around a single alternative to Mr. Romney.
Mr. Huntsman becomes the fourth announced Republican candidate to drop out of the race. Herman Cain dropped his bid in December amid accusations of sexual misconduct. Tim Pawlenty, the former governor of Minnesota, dropped out shortly after a disappointing finish in the Iowa straw poll this summer. Representative Michele Bachmann of Minnesota left the race after finishing last in Iowa.
Michael D. Shear contributed reporting.