Donald Trump has easily won the Republican caucuses in Michigan, where the party has been riven by infighting that some Republicans fear could hurt his campaign in the key battleground state as he gears up for the general election in November.

The former US president also won the Missouri and Idaho Republican caucuses on Saturday, according to Edison Research.

In all three states Trump trounced Nikki Haley, his last remaining rival for the Republican presidential nomination, moving him closer to becoming his party’s White House standard-bearer and a likely general election rematch with President Joe Biden, a Democrat.

In Michigan, Trump beat Haley in all 13 districts taking part in the nominating caucuses, according to the state Republican Party.

Overall, Trump won with nearly 98 per cent support: 1575 votes to just 36 for Haley.

Pete Hoekstra, the Michigan Republican Party’s chair, called it an “overwhelming, dominating victory”.

More than 1600 party insiders participated in the presidential caucus in the western Michigan city of Grand Rapids, where they were choosing delegates for Trump or former UN Ambassador Haley for the party’s national nominating convention in July.

Haley is fast running out of time to alter the course of the Republican nominating race. Next up this week is Super Tuesday, the biggest day in the primaries, when 15 states and one territory will vote.

With victories in Iowa, New Hampshire, Nevada, the US Virgin Islands, South Carolina, and now Michigan, Missouri and Idaho under his belt, Trump is far and away the frontrunner in the race, with Haley hanging on thanks to support from donors keen for an alternative to the former president.

The contest in Michigan on Saturday had held the potential for confusion. Internal turmoil has been percolating in the party for months, pitting backers of Michigan’s former Republican Party chair, Kristina Karamo, against the faction of party members who voted to oust her on January 6, and installed Hoekstra as chair.

Hoekstra, whom Trump backed as chair, was overseeing the convention in Grand Rapids. Karamo had been planning to chair a duelling convention in Detroit on Saturday, but that was cancelled after a Michigan court this week affirmed her ouster and an appeals court denied her request to stay the ruling.

Trump’s victories in Missouri and Idaho netted him 54 and 32 delegates respectively.