Five days before the South Carolina primary, Jon Huntsman dropped out of the presidential race Monday and endorsed Mitt Romney for the party's nomination, becoming the latest Republican to call the GOP front-runner the strongest candidate to beat the Democratic incumbent.
"I believe it is now time for our party to unite around the candidate best equipped to defeat Barack Obama," Huntsman said at a news conference, his family by his side. "Despite our differences and the space between us on some of the issues, I believe that candidate is Gov. Mitt Romney."
The development added to the aura of inevitability Romney has worked to create in South Carolina and the race at large.
But Huntsman's departure and endorsement of Romney seemed unlikely to clarify the overriding question of the Republican campaign: Whether conservative voters could or would unify behind Rick Santorum, Newt Gingrich or Rick Perry to create a strong conservative challenger to the former Massachusetts governor.
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It also prompted at least one Perry backer to urge the Texas governor to abandon his bid in hopes of preventing conservative voters from dividing their support among several candidates and handing Romney a win.
"There are a lot of conservatives who were happy to see him get in and now who would be happy to see him get out," state Sen. Larry Grooms, an early Perry supporter, said. "When conservatives have split in the past, we end up nominating a moderate, and that's not good for our party."
In South Carolina, the eventual effect of the Huntsman endorsement is unclear.
He barely had a campaign organization here and was all but broke, with big donors fleeing long ago. Huntsman, considered the moderate in the race because of his support for civil unions and other positions that don't sit well with the right flank, was in the low single digits in polls.
But those who had planned to vote for him are more likely to shift their votes to Romney rather than one of his more conservative rivals. Polls show Romney was most often the second choice of Huntsman backers. Both candidates have emphasized their business backgrounds and have espoused socially moderate positions in a state where social conservatives are an influential bloc. Both also are Mormons.
"Certainly, it will help Gov. Romney here, it's just not clear how much," said former state Attorney General Henry McMaster. An early Huntsman supporter, McMaster had not committed to another candidate after Huntsman's announcement.
Romney is leading in South Carolina polls — followed by Gingrich, with Santorum and Texas Rep. Ron Paul fighting for third and Perry trailing — as he pushes toward three straight victories after winning Iowa and New Hampshire earlier this month. A South Carolina triumph would give Romney significant momentum heading into Florid, next up on Jan. 31, and he's banking on getting a boost from South Carolina Gov. Nikki Haley and Arizona Sen. John McCain, winner of the 2008 primary in a state that has voted for the eventual GOP nominee since 1980.
With the primary looming Saturday, Romney's rivals dismissed Huntsman's endorsement.
"Moderates are backing moderates," Santorum, a former Pennsylvania senator, said at a Columbia appearance. "No surprise there."
Gingrich, the former House speaker locked in a bitter battle with Romney, said at an event in Myrtle Beach: "Why would you want to nominate the guy who lost to the guy who lost to Obama?"
Huntsman's endorsement comes just two days after Santorum emerged as the consensus, if not unanimous, choice of a group of national Christian political activists who met over the weekend in a last-ditch effort to rally conservatives.
In recent days, pressure has been increasing on Perry, who registers in the single digits in polls here, to leave the race to allow South Carolina's influential social conservatives to unify behind Santorum or Gingrich.
"It's important that we eventually consolidate this race," Santorum said Monday. But he stopped short of adding his voice to those suggesting Perry drop out, saying: "That's up to the candidates themselves to decide."
On Sunday, conservative author Eric Metaxas indirectly suggested Perry should quit the race while speaking at a packed prayer breakfast in Myrtle Beach. The night before he had tweeted: "Dear Gov. Perry: Do the right thing for your country; endorse Rick Santorum before the SC primary next Saturday ... you'll wish you had."
Katon Dawson, Perry's South Carolina chairman, resisted the idea that there was a drumbeat for Perry to quit.
"I find it sort of offensive that some Republicans would tell us they want to hand-pick the candidate before the election," Dawson said.
And Ralph Reed, founder of the national Faith and Freedom Coalition, also said he knew of no effort by the conservative leaders who met Saturday in Texas to urge Perry to quit.
"We have never asked any candidate to drop out of the race publicly or privately. And we will not do so," Reed said.
In Iowa two weeks ago, some evangelical pastors and conservative leaders had asked Minnesota Rep. Michele Bachmann to consider ending her campaign to allow a conservative to emerge. She did not, and Romney edged Santorum in Iowa by a razor-thin eight votes. She later quit the race.
With Perry showing no signs of departing, Santorum faces the added burden of a barrage of attack ads by an independent group that supports Romney's campaign. The group, Restore Our Future, was running almost $900,000 worth of advertising this week, more than any of the candidates' campaigns and all of it against Santorum.
Santorum complained Monday about the ads, which accuse him of having supported pork-barrel spending in Congress and supporting voting rights for felons. Santorum has defended his support for that spending. And he said Monday he supports allowing felons who have completed their sentences to apply to have their voting rights restored, a policy that is law in 48 states.
Restore Our Future spent roughly $3 million on similar anti-Gingrich ads in the final month of the Iowa campaign and was seen as contributing to Gingrich's fourth-place finish in the caucuses.
A similar group that supports Gingrich was running roughly $850,000 in ads against Romney.