In the first Republican contest of the season, the two candidates were separated much of the night by only a sliver of votes, with Mr. Romney being declared the winner by eight ballots early Wednesday morning.
But the outcome offered Mr. Santorum a chance to emerge as the alternative to Mr. Romney as the race moves to New Hampshire and South Carolina without Gov. Rick Perry, who announced that he was returning to Texas to assess his candidacy, reports The New York Times.
“Game on!” Santorum declared to cheering supporters as votes trickled in after the agonizingly close contest. “People have asked me how I’ve done this,” he said. “I survived the challenges so far by the daily grace that comes from God.”
“Being here in Iowa has made me a better candidate,” Mr. Santorum said, arriving at a caucus in Clive, where he urged Republicans to vote their conscience. “Don’t sell America short. Don’t put someone out there from Iowa who isn’t capable of doing what America needs done.”
Mr. Santorum now faces a challenge of trying to broaden his campaign organization on the fly to compete with the structure that Mr. Romney has spent years building. His aides said he will campaign this week in New Hampshire and South Carolina, vowing to compete with Mr. Romney everywhere.
The Iowa caucuses did not deliver a clean answer to what type of candidate Republicans intend to rally behind to try to defeat President Obama and win back the White House. With 99 percent of the vote counted, Mr. Santorum and Mr. Romney, whose views represent the polar sides of the party, each had 24.6 percent.
“Onto New Hampshire, let’s get that job done!” Mr. Romney told supporters at a late-night rally, when he was five votes shy of Mr. Santorum. “Come visit us there, we’ve got some work ahead.”
According to Reuters, after the bruising contest, at least one candidate, Texas Governor Rick Perry, indicated his presidential bid may be over.
“I’ve decided to return to Texas, assess the results of tonight’s caucus, determine whether there is a path forward for myself in this race,” Perry said after a disappointing fifth place finish.
Representative Ron Paul of Texas was a close third on Tuesday with 21 percent of the caucus votes.
“We will go on,” he said in an upbeat speech. “There is nothing to be ashamed of.”
Paul’s unorthodox views, including supporting a return to the gold standard and an end to a U.S. overseas military presence, have won him a passionate following among voters who feel deeply alienated from more mainstream candidates. He will have an uphill climb translating that into wider support among Republicans.
“Protecting your personal rights and your economic rights are what the government’s supposed to do, they’re not supposed to run our lives or spend our money,” he told supporters.
Newt Gingrich was in fourth place with 13 percent of the votes, followed by Mr. Perry with 10 percent and Representative Michele Bachmann of Minnesota with 5 percent.
“There will be a great debate in the Republican Party before we are prepared to have a great debate with Barack Obama,” Mr. Gingrich said, pledging to raise the intensity of his criticism of Mr. Romney before the next contests.
About 120,000 participated in Tuesday’s Republican vote, and another 25,000 participated in the Democratic caucus — about 8 percent of the state’s eligible voters.
Many caucusgoers did not make up their minds until late; entrance polls indicated that nearly half had decided whom to support within the last few days. Mr. Santorum was the candidate who benefited the most from these late-deciders — a third of them backed him.