The chairman of the Iowa Republican party has said Mitt Romney has won the Iowa caucus by eight votes.
Chairman Matt Strawn made the announcement of the razor-thin margin in the opening contest in the campaign to pick a challenger to President Barack Obama in Des Moines.
Mr Romney, former governor of Massachusetts, narrowly edged out former Pennsylvania senator Rick Santorum.
Mr Strawn said Mr Romney received 30,015 votes and Mr Santorum 30,007.
No matter how close the final results in Iowa, there were no plans for a recount.
Iowa has an uneven record when it comes to predicting national winners. It sent Mr Obama on his way in 2008, but eventual Republican nominee John McCain finished a distant fourth to former Arkansas governor Mike Huckabee.
The 100,000 or so voters in the Republican caucuses are disproportionately white and more conservative than the overall American electorate.
Unlike in a primary, in which voting occurs over hours, the Iowa caucuses were meetings held in schools, churches and other locations where Republicans gathered for an evening of politics.
Each presidential candidate was entitled to have a supporter deliver a speech on his or her behalf before straw ballots were taken.
Mr Romney, who finished second in Iowa in 2008 despite a costly effort, initially campaigned cautiously this time around. But that changed in the race’s final days as he pursued a first-place finish, running as a conservative businessman with the skills to fix the economy.
This time, he drew a smaller share of the vote than the 25.2% he received in 2008.
His rivals argued that he was not nearly conservative enough on the economy and social issues such as abortion and gay rights.
Democrats watched carefully in a state that has swung between the two parties in recent presidential elections.
Mr Obama was unopposed for his party’s nomination. Even so, his re-election campaign set up eight offices across Iowa, made hundreds of thousands of calls to voters and arranged a video conference for the president with caucus night supporters.
“This time out is going to be in some ways more important than the first time,” he told Democrats across the state. “Change is never easy.”
The state’s lead-off spot has been a fixture for decades. Democrats moved the caucuses up to early January in 1972, and Republicans followed suit four years later.