Discord in G.O.P. as Conservatives Air Differences MYRTLE BEACH, S.C. - With new calls on Monday for Republicans to rally around Mitt Romney as their presidential nominee, some conservatives showed new signs of fracturing despite a vote over the weekend by religious leaders to coalesce behind Rick Santorum as an anti-Romney alternative. Jon M. Huntsman Jr., the moderate former governor of Utah whose candidacy did not live up to its early promise, dropped out of the race and endorsed Mr. Romney, saying, "It is now time for our party to unite around the candidate best equipped to defeat Barack Obama. Mr. Huntsman said. But his call for unity came as evangelical leaders, intent on blocking Mr. Romney's path to the nomination, showed new divisions after having appeared on Saturday to settle on Mr. Santorum as their conservative choice. Four conservative Christian leaders who attended a meeting of evangelicals in Texas asserted their independence on Monday, issuing a statement that said, "Many there were and still are for Newt Gingrich." Underscoring the party's lack of unity, Mr. Santorum's campaign released its first negative advertisement against Mr. Romney hours before the candidates gathered here for a debate. The ad called Mr. Romney, a former governor of Massachusetts, "more liberal than Ted Kennedy on social issues" and said he had inspired President Obama's health care overhaul, meaning he would be unable to present a sharp contrast with Mr. Obama. The ad highlighted how the battle for South Carolina's evangelical and conservative voters - who make up 60 percent of the state's registered Republicans - has boiled down to a two-man contest between Mr. Santorum and Mr. Gingrich. Neither candidate showed any sign that he was considering stepping aside. As Mr. Santorum was trying to build momentum from Saturday's vote by the religious leaders, the Gingrich camp sought to burst that bubble, saying that the Santorum team had misrepresented the scope of the evangelicals" support and that it would not matter anyway. Mr. Gingrich told voters at a stop here: "People have to decide: if you vote for Senator Santorum, in effect you're functionally voting for Governor Romney, because he's not going to beat him. Still to be determined is whether Mr. Huntsman's endorsement would help Mr. Romney, who was leading in most polls here. Mr. Huntsman said Republicans now must focus on defeating President Obama in November, which is why they needed to join in supporting Mr. Romney as their nominee. But with many voters still undecided or concerned about Mr. Romney's conservative credentials, the endorsement may sway few people. As the campaigning in South Carolina intensified, the Santorum team stepped up efforts to corral social conservatives into its fold and planned to roll out more endorsements from individual evangelical and conservative leaders in the coming days. "In the next day or so, several groups will be contacting hundreds of thousands, if not millions, of people by e-mail and robocalls, encouraging them to support Santorum," said Colin Hannah, the president of the conservative advocacy group Let Freedom Ring, who attended the Texas meeting. "I think we're going to see a substantial response," Mr. Hannah said. In a conference call late Monday afternoon with about 30 of the evangelical leaders who had attended the Texas meeting, Mr. Santorum discussed the nuts and bolts of how they would organize their support for him. Both Mr. Gingrich and Mr. Santorum have invested considerable time and money here and see South Carolina as their firewall. Whoever does worse on Saturday is likely to face renewed pressure to drop out, but both men were already laying the groundwork for the next contest, in Florida on Jan. 31. The impact of the evangelicals" vote for Mr. Santorum was already being felt. John Stemberger, president of Florida Family Action, which has helped lead efforts against same-sex marriage, became one of the first evangelical leaders to announce on Monday that the Texas meeting had changed his mind. He had been co-chairman of the Florida campaign for Gov. Rick Perry of Texas going into the meeting, but by the final ballot he supported Mr. Santorum. Mr. Stemberger said he believed that Mr. Perry was "not resonating" and that conservatives needed to be united.