Trump wins Iowa caucus, taking first step toward Biden rematch

Donald Trump captured the first 2024 Republican presidential contest in Iowa on Monday, according to Edison Research projections, as he seeks a third consecutive nomination.

Florida Governor Ron DeSantis and former UN Ambassador Nikki Haley were in a battle for second place as they sought to emerge as the chief alternative to Trump, who served as president from 2017-2021, Edison projected.

Trump appeared likely to win by a record-setting margin, based on early results, which would bolster his argument that he is the only Republican candidate capable of taking on Democratic President Joe Biden, despite facing four criminal cases that could go to trial before the November 5 general election.

With 34 per cent of the expected vote tallied, Trump had 51.9 per cent of the vote, while DeSantis was at 20.7 per cent and Haley 19 per cent. The largest margin of victory for an Iowa Republican caucus was 12.8 percentage points for Bob Dole in 1988.

Both DeSantis and Haley were aiming for a strong second-place finish that could demonstrate they might prevent Trump's march toward the nomination.

DeSantis in particular had wagered his campaign on Iowa, barnstorming all of its 99 counties, and a third-place finish could increase pressure for him to end his bid.

Polls show him far behind Trump and Haley in the more moderate Northeastern state of New Hampshire, where Republicans will choose their nominee eight days from now.

Iowans braved life-threatening temperatures to gather at more than 1,600 schools, community centres and other sites for the state's first-in-the-nation caucus, as the 2024 presidential campaign officially got under way after months of debates, rallies and advertisements.

Caucus-goers appeared broadly supportive of Trump, according to an Edison entrance poll.

DeSantis and Haley had expressed confidence they would exceed expectations in Iowa, though neither predicted victory.

"If you're willing to brave the cold and turn out for me, I'll be fighting for you for the next eight years, and we're going to turn this country around," DeSantis told a crowd earlier in the day in Sergeant Bluff.

At a diner in Des Moines, Haley predicted that other candidates will be forced to drop out in the weeks to come. "This will be a two-person race with me and Donald Trump," she told supporters.

Iowa Democrats did not vote on Monday for their presidential nominees because the party has reshuffled its nominating calendar to put states with more diverse populations ahead of Iowa this year. They will cast their ballots by mail, with the results to be released in March.

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.

A political battleground that backed Democrat Barack Obama in 2008 and 2012, the state is now seen as reliably Republican in presidential elections as registered Republicans edge out Democrats.