Donald Trump has secured a resounding win in the first 2024 Republican presidential contest in Iowa, asserting his command over the party despite facing scores of criminal charges.
Trump took more than half the votes, propelling him towards what looks set to be a close and deeply acrimonious election campaign against President Joe Biden, a Democrat, in November.
Florida Governor Ron DeSantis, 45, finished well behind Trump in second place in Iowa, edging out former UN ambassador Nikki Haley, 51, as they both failed to emerge as the chief opponent.
Trump, 77, the only current or ex-US president to be charged with criminal activity, won by an unprecedented margin for an Iowa Republican contest, strengthening his case that his nomination is a foregone conclusion given his massive lead in national polls.
Trump garnered 51 per cent, DeSantis 21 per cent and Haley 19 per cent, with 99 per cent of the expected vote tallied, according to Edison Research. That victory margin far surpassed the previous record of 12.8 percentage points for Bob Dole in 1988.
"THANK YOU IOWA, I LOVE YOU ALL!!!" Trump wrote on his social media platform, Truth Social.
Entrepreneur Vivek Ramaswamy ended his long-shot presidential bid after winning just under eight per cent of the vote on Monday, and he endorsed Trump.
The candidates immediately move on to New Hampshire on Tuesday. The state's more moderate Republicans will choose their nominee next Tuesday and polls show Trump with a smaller lead over Haley there, and DeSantis far behind.
Trump's performance in Iowa showed his enduring popularity among Republican voters even after the January 6, 2021, attack on the US Capitol by a mob of his supporters.
He is also fighting 91 criminal charges for trying to overturn the 2020 election, retaining classified documents after leaving the White House and falsifying records over hush money payments to a porn star.
Nearly two-thirds of Iowa caucus-goers embraced Trump's false claims about voter fraud in the 2020 presidential election, saying they did not think Biden legitimately beat Trump.
More than 60 per cent said Trump would still be fit to serve as president even if convicted of a crime.
Both DeSantis and Haley vowed to press ahead, ensuring Trump's opposition will remain fractured as the campaign moves on.
"We've got our ticket punched out of Iowa!" DeSantis, who had staked a lot on a strong performance in the state, told supporters in West Des Moines on Monday.
"When you look at how we're doing, in New Hampshire, in South Carolina and beyond, I can safely say tonight Iowa made this Republican primary a two-person race," Haley said on Monday night.
Trump has aimed to create an air of inevitability around his campaign, skipping all five of the Republican debates thus far and largely eschewing the county-by-county politicking that most candidates do ahead of the Iowa vote.
"Trump is very narcissistic, he's very cocky, but he's going to get stuff done," said Rita Stone, 53, a Trump backer, who attended a caucus at a West Des Moines high school.
Like many other voters, Stone said her leading concern was the US southern border with Mexico, praising Trump's effort to build a wall when he was president.
Iowa has historically played an outsized role in presidential campaigns due to its early spot on the campaign calendar.
But the winner of Iowa's Republican caucuses did not go on to secure the nomination in the last three competitive contests in 2008, 2012 and 2016.
