OSKALOOSA, Iowa » Fearing that Republicans will ultimately nominate an establishment presidential candidate like Jeb Bush, leaders of the nation’s Christian right have mounted an ambitious effort to coalesce their support behind a single social-conservative contender months before the first primary votes are cast.

In secret straw polls and exclusive meetings from Iowa to California, the leaders are weighing the relative appeal and liabilities of potential standard-bearers like Sen. Ted Cruz of Texas, Gov. Bobby Jindal of Louisiana and former Govs. Rick Perry of Texas and Mike Huckabee of Arkansas.

"There’s a shared desire to come behind a candidate," said Tony Perkins, the president of the Family Research Council, a national lobbying group that opposes abortion and equal rights for gays.

"It would be early for a group of leaders to come out for a candidate, but not too early for the conversations to begin," he said.

The leaders of evangelical and other socially conservative groups say they do not believe that Bush, the former governor of Florida — whom they view as the preferred candidate of the Republican Party’s establishment — would fight for the issues they care most about: opposing same-sex marriage, holding the line on an immigration overhaul and rolling back abortion rights.

The efforts to coalesce behind an alternative candidate — in frequent calls, teleconferences and meetings involving a range of organizations, many of them with overlapping memberships — are premised on two articles of conservative faith: Republicans did not win the White House in the past two elections because their nominees were too moderate and failed to excite the party’s base. And a conservative alternative failed to win the nomination each time because voters did not unite behind a single champion in the primary fight.

This time, social conservatives vow, will be different. They plan to unify behind an anti-establishment candidate by summer or early fall, with the expectation that they will be able to overcome any fundraising advantage of the Republican elite by exerting their own influence through right-wing talk radio and social media, and by mobilizing an army of like-minded small donors.

"Conservatives smell blood in the water," said Kellyanne Conway, a Republican pollster who has participated in the vetting. "They feel they’ve got the best shot to deny the establishment a place."

Conway said the candidates seen as having potential to energize the party’s right wing would be invited to make their case before national groups of social conservatives in the coming weeks and months.

Richard Viguerie, the conservative direct-mail pioneer, said he was involved in the effort to rally behind a candidate so "we won’t go into this season divided six or eight different ways."

Otherwise, he said, "It’s going to make it very difficult to stop the establishment’s candidate, i.e., Jeb Bush."

Of course, the basic premise driving the conservatives’ effort — that Republicans have a better shot at the White House by nominating a hard-right candidate who excites the grass-roots — is rejected by the party’s establishment, which views a hard-line nominee as a recipe for a crushing defeat in 2016.

A spokesman for Bush declined to comment.

Some on the Christian right remain skeptical of the effort to settle on a single socially conservative candidate. Similar attempts in 2008 and 2012 collapsed because no consensus was reached, they say. And it is unclear what impact an endorsement by national social conservatives would have on a primary competition that will probably be driven by abundant outside money, debate performances and long months of retail campaigning.

"I think it’s a useless process," said David Lane, who arranges expenses-paid meetings of conservative pastors to hear from potential candidates, most recently at a gathering in Des Moines, Iowa, where Cruz and Jindal spoke. "My goal is to give the constituency access to candidates, then let them decide."

But participants in the effort say that the lessons of recent elections have sunk in, and that this time they will not allow their debate to devolve into discord.

"I think everybody understands — more, even, at the grass-roots level — that there has been a pattern, and the pattern needs to be broken," said Gary L. Bauer, a conservative activist and a former presidential candidate. He led an effort called the Arlington Group that tried to galvanize support for a social conservative standard-bearer in the 2008 and 2012 elections.

The yearning for a single conservative contender to unite behind was perhaps most in evidence last month, when a dozen leaders of evangelical and other groups gathered for a half-day conference to discuss possible candidates in Dana Point, Calif.

The retreat, at the five-star St. Regis Monarch Beach resort, was the latest in a series organized by Perkins, of the Family Research Center, according to people briefed about the proceedings.

The session culminated in a vote for "the most viable candidate." The result, projected on a screen at the front of a conference room, showed Huckabee, a former Baptist preacher, as the winner. In a three-way tie for second were Perry, Jindal and Gov. Scott Walker of Wisconsin, according to a cellphone photo of the results shared with The New York Times.

The Feb. 19 session in Dana Point came more than a month before Cruz, the son of a fiery conservative pastor, generated a flurry of attention by formally declaring himself a candidate for president.

But on Sunday, after news broke of Cruz’s impending announcement, there were signs here in Oskaloosa, a farming town in central Iowa, that grass-roots conservatives had taken notice of him.

"Ted Cruz, there’s a fire inside of him," said Julie Tvedt, the administrator of the Jubilee Family Church, who met for lunch with 12 other Republican evangelical activists after church.

"I really like his backbone," said Curt Block, a salesman. "Compromise is one thing, but when you’re compromising everything, for what are you even standing?"

The instant gravitation toward Cruz here could be significant, or it could be momentary — in which case the efforts of national leaders to settle on a candidate for the Christian right could prove misguided. After all, voter sentiment shifts quickly, and sometimes mysteriously, and endorsements by authority figures are often of dubious value.

"No question that conservative leaders around the country would love to coalesce around a candidate," said Bob Vander Plaats, a social conservative leader in Iowa. "But it’s easier said than done."

At the recent gathering of pastors in Des Moines, Jindal curried favor on one of their top issues: opposition to same-sex marriage. "I know it is popular to evolve on this issue," he said. "I’m not evolving."

His first questioner was a woman who asked if Jindal and other socially conservative contenders could decide among themselves who should be the one true standard-bearer.

Her tone was heartfelt, even desperate. "I would love to see you godly leaders pray and fast and see who God would be anointing to raise up," she said. "We would rally behind him. We cannot be so divided. Our money, our time, our loyalty is so divided."

To which Jindal offered a one-word response: "Amen."