- Mike Wendling, Bernd Debusman Jr. & Holly Honderich
- BBC News, Iowa
Florida Gov. Ron DeSantis finished second in Iowa's caucuses, pushing former UN ambassador Nikki Haley into third place in a Republican race dominated by Donald Trump.
Mr DeSantis campaigned relentlessly in the state, but he finished a long way behind the former president.
With nearly all the votes counted, Mr Trump has 51% of the vote, Mr DeSantis has 21% and Ms Haley has 19%.
Iowa is the first state where Republican voters choose their White House.
Their election is called a caucus because people must be present in person at a specific time and place to vote.
The party's eventual nominee, who will challenge the Democratic Party's choice in the November election, is almost certainly President Joe Biden.
At a victory ceremony in the state capital, Des Moines, Mr Trump hailed a special night and urged Americans to come together to “set the world straight”.
He said he would “seal the border” in the face of an “invasion” and called Joe Biden the worst president in the country.
Registered Republicans gathered across Iowa Monday evening at churches, schools, gyms and community centers to vote.
Mr Trump is the favorite to win Iowa and former WWE wrestler Glenn Jacobs, who is campaigning for Mr Trump, has predicted a big win.
Speaking to the BBC an hour before voting began in Des Moines, he said the country was headed in the wrong direction, citing the border crisis and US intervention in the Middle East.
At a high school in Davenport, in the eastern part of the state, Brian Romer, a Trump supporter, gave a fiery speech to his fellow Republicans in support of the former president.
“The things that happen in this country are the things that happen in communist countries,” he said, referring to Mr Trump's criminal charges. “We no longer live in a free country.”
But both Mr. DeSantis and Ms. Haley, the former governor of South Carolina and the U.S. ambassador to the United Nations under President Trump, said on Monday night that political winds were in their way.
“They threw everything at us except the kitchen sink,” Mr DeSantis said. “The media was against us, they wrote our obituary months ago.
“Despite all that… we got our ticket from Iowa.”
Kyle Brock rallied support for Mr DeSantis at Grand Ragan Elementary School in the Des Moines suburb of Waukee, arguing it was time for Republicans to move on from Mr Trump.
“I like him [the Florida governor’s] “The integrity, and the way he presents himself and — really — what he did in Florida,” he said.
Mr. DeSantis spent most of his time and resources in Iowa, campaigning in all 99 counties and courting the rural state's influential evangelical voters.
But the conservative Florida governor could face tough terrain next week in the more moderate state of New Hampshire, where his primary is.
Ms. Haley, who has an outside chance of defeating Mr. Trump in the state, said she has momentum.
But his third-place finish seemed disappointing for a candidate who was tipped to advance beyond the caucuses.
Haley Still-Carris, who attended the caucus at Roosevelt High School in Des Moines, said Ms. Haley had a good chance of winning in November.
“I look at the other Republican candidates and President Biden, and I think he's electable. That's what we need — less drama and less chaos.”
Biotech entrepreneur Vivek Ramaswamy has announced he is suspending his presidential campaign after he appeared to be on course for a fourth-place finish. He supported Mr Trump.
In a post on X, Mr Biden appeared to be headed for a rematch with Mr Trump.
“But here's the thing: This election is always going to be you and me and the extreme mega-Republicans,” the Democratic leader wrote. “It was true yesterday, it will be true tomorrow.”
More about the US election
According to exit poll data, Mr Trump received strong support from white evangelicals and more conservative voters.
He won broadly among men, women, older voters and younger voters, improving on his 2016 performance in all these groups.
Even as Mr Trump faces four separate criminal investigations, he has cemented his lead among Republicans in national polls.
He faces sentencing as soon as this month in a civil fraud trial that threatens his New York property empire. He is expected to attend another hearing on Tuesday, which will determine how much defamation damages he should pay E Jean Carroll, the woman he allegedly sexually assaulted.
After New Hampshire next week, voters in Nevada and South Carolina will have their say in the Republican race in February.