By effectively tying Mr. Romney in Iowa, Mr. Santorum, a former senator from Pennsylvania, has persuaded some influential evangelicals to give him another look. But others argue that only Newt Gingrich — who, like Mr. Santorum, is a conservative Roman Catholic — has the campaign resources and intellectual heft to win. A few still think that Gov. Rick Perry of Texas, who is not actively campaigning in New Hampshire but plans to contest the primary in South Carolina on Jan. 21, should stick around in case the other two burn out. Both Mr. Perry and Mr. Santorum are headed to South Carolina on Sunday…

“It’s way too early to panic,” said David Barton, a Christian author and political strategist who has been a consultant to several candidates. “If leaders did endorse one candidate, I think they’d wind up being ignored by their followers.”…

Even after the Florida primary on Jan. 31, it should be “arithmetically possible” for one of the more conservative candidates to wrest the nomination from Mr. Romney, said Ralph Reed, the chairman of the Faith and Freedom Coalition. But three stiff conditions would have to be met, he said: a largely unified social conservative vote, adequate financing for primaries that in some states require $2 million per week for television advertisements, and decent local campaign infrastructures.