DES MOINES — Senator Ted Cruz of Texas, powered by a surge of support from evangelical Christians, dealt a humbling loss to Donald J. Trump in the Iowa caucuses on Monday, throwing into question the depth of support for Mr. Trump’s unconventional candidacy.
In the first contest of what so far has been more a populist revolt against the political order than a traditional Republican primary, Senator Marco Rubio of Florida finished a strong third, bolstering his case to consolidate the support of Republicans uneasy about the two top finishers.
With 98 percent of precincts reporting, Mr. Cruz had nearly 28 percent of the vote, Mr. Trump 24 percent and Mr. Rubio 23 percent.
Mr. Cruz’s victory was hard-earned. He fought off a barrage of attacks in the campaign’s final weeks from Mr. Trump as well as from Iowa’s longtime governor, Terry E. Branstad, and Republican leaders in Washington who warned that the hard-line Mr. Cruz would lead the party to electoral disaster this fall.
Having felled the brash Mr. Trump, who unceasingly predicted victory and dominated the race up until the first voting, Mr. Cruz can credibly portray himself, to conservatives who have yearned to unite behind a strong champion, as a giant-killer.
“To God be the glory,” Mr. Cruz told jubilant supporters. “Tonight is a victory for the grass roots. Tonight is a victory for courageous conservatives all across Iowa and our great nation.”
The close race illustrated just how turbulent the Republican race may be, with the vote fragmenting between Mr. Cruz’s evangelicals and Tea Partyadherents, Mr. Trump’s blue-collar political newcomers and Mr. Rubio’s mix of conservatives and pragmatic Republicans hungry for victory.
Turnout was about 185,000, a record, according to Edison Research, which conducted entrance polls at precincts across the state. Mr. Trump’s success had been expected to hinge on whether he could mobilize his supporters. But the turnout was not enough to deliver him a win, even though 46 percent of those who turned out were participating in a Republican caucus for the first time.
Instead, Mr. Trump paid the price for building only a rudimentary political organization in the state: The brew of energy and anger powering his candidacy did not fully translate into votes.
“I love you people. I love you people,” a subdued-sounding Mr. Trump unconvincingly told a crowd of Iowans in West Des Moines. “We will go on to get the Republican nomination, and we will go on to easily beat Hillary or Bernie or whoever the hell they throw out there.”
Mr. Trump’s celebrity-fueled airplane hangar rallies proved no match for Mr. Cruz’s fervent appeal to Christian values in winning over Iowa’s evangelical voters, who made up nearly two-thirds of those who did show up to caucus. Mr. Cruz won about a third of the evangelical vote.
That achievement was even more remarkable given the competition Mr. Cruz also faced from Mr. Rubio and Ben Carson, the spiritually minded retired neurosurgeon, among others. When Mike Huckabee and Rick Santorum won the Iowa caucuses in 2008 and 2012, respectively, they did so without formidable opposition for those voters. (Each ran again this year but failed to earn significant backing.)
The victory for Mr. Cruz also was a validation of the Iowa tradition that success here comes from intensive retail campaigning. He built an extensive organization and spent months visiting each of Iowa’s 99 counties.
The throngs of Iowans who came to see Mr. Trump’s improvisational performances, by contrast, may have come away entertained, but not enough of them seemed persuaded that he was presidential.
The question for Mr. Cruz now is whether to compete aggressively in New Hampshire, which votes next Tuesday, or divide his time between there and the next battleground, South Carolina, which holds its primary on Feb. 20 and has an evangelical population closer in size to Iowa’s.
Mr. Cruz has trailed well behind in recent New Hampshire polls, but Mr. Trump, his aura of invincibility gone, could prove vulnerable there as well. Should Mr. Cruz — whose $19 million war chest is the most money of any Republican candidate — find success with that state’s more secular voters, it would signal that he has the potential to unite a wider Republican electorate.
Yet the strong Iowa finish by Mr. Rubio, the choice of a plurality of voters who said they made their decisions in the last week, will allow him to begin making the case to Republican donors, activists and elected officials that he is the strongest candidate acceptable to them who can win over grass-roots conservatives.
Mr. Rubio’s late surge was a vindication of his strategy: He waited to aggressively compete in Iowa until January, when he crisscrossed the state furiously with 36 events in the final four weeks.
Portraying his third-place showing in the best possible light, Mr. Rubio subtly took aim at both Mr. Cruz and Mr. Trump on Monday, suggesting they could not defeat Mrs. Clinton.
“When I’m the nominee, we are going to unify our party and we are going to unify the conservative movement,” Mr. Rubio said to hundreds of supporters in Des Moines.
While Mr. Cruz, a pastor’s son, counted on Christian conservatives, Mr. Rubio aggressively tried to woo that constituency, too. He ran an ad in which he spoke of “the free gift of Salvation offered to us by Jesus Christ.” And in the final debate before the caucuses, held Thursday in Des Moines, he notably referred to “Jesus Christ, who came down to earth and died for our sins.”
With the top finishers a businessman who had never run for office and two first-term senators, governing experience evidently mattered little to Iowans. The five current or former governors still running won a combined 8 percent — less than what the retired neurosurgeon Ben Carson received, even after his campaign nearly unraveled in the weeks before the caucuses.
After months of watching vast crowds wait hours in line to fill gymnasiums, many Iowans thought Mr. Trump’s star power would shatter turnout records. It may have helped.
But it was Mr. Cruz who benefited most. He won support from local conservative leaders, including Representative Steve King. And as Mr. Trump began to assail him, Mr. Cruz delivered sharp counterattacks over Mr. Trump’s past liberal views, particularly on abortion rights.
Mr. Cruz was also helped by Mr. Trump’s self-inflicted wounds. In recent weeks, Mr. Trump spoke of the New Testament’s Second Book of Corinthians as “Two Corinthians,” a telling lapse in the eyes of evangelicals. He proclaimed that he could shoot somebody on Fifth Avenue in Manhattan and still “wouldn’t lose voters.” And Thursday, Mr. Trump skipped the only Republican debate held in Iowa to avoid a confrontation with Mr. Cruz and Fox News. It was enough to make Iowans uneasy.
Perhaps most critically, though, Mr. Trump lacked the organization that Mr. Cruz had put into place in Iowa. Given his reliance on voters new to the caucus process, Mr. Trump needed a robust get-out-the-vote operation. But he was badly out-organized by Mr. Cruz, who relied on scores of church pastors and brought in hundreds of volunteers from as far as Idaho and Texas.
Instead, Mr. Trump ran a campaign in his own self-regarding image. He defied history’s lesson that the caucuses are won through one-on-one campaigning and humble requests of support. There were no community round-tables, no bus tour through courthouse towns and little in the way of unscripted interaction with voters outside of posing for pictures and signing autographs.
What Iowa rituals Mr. Trump did submit to had a novelty quality to them, as when he made a show of stopping in at a Pizza Ranch restaurant, a campaign trail staple, and once stayed overnight at a Holiday Inn Express (“Good mattress,” he said).
And when he indulged in the pandering to Iowa institutions that is typical of political supplicants here, he did so in his exaggerated, almost comic style — as if he were playing the role of presidential candidate.
“I am a great Christian,” he assured Iowa’s voters who may have been skeptical about a thrice-married New York casino magnate. Mr. Trump also vowed to support “the ethanol,” referring to the federal biofuel subsidies prized by the agriculture industry here, while occasionally musing that he might just buy a farm in Iowa. And when Senator Charles E. Grassley came to one of his rallies, Mr. Trump did not evince much knowledge about the senator’s 40-year tenure in Congress but did say “this is a great guy, this is a great guy.”
In the final weekend, every public poll showed Mr. Trump winning. But Mr. Trump’s problems were registering with Mr. Cruz’s camp.
Mr. Cruz’s campaign manager, Jeff Roe, was coolly confident. Late Sunday, he nonchalantly assured a reporter of victory, saying that Mr. Trump was sliding and might even finish third.