Former US president Donald Trump swept the latest Republican presidential nominating contest on Saturday, beating rival Nikki Haley in Missouri.

Associated Press called the Missouri race for Trump with only a small percentage of the votes reported. Republicans in Idaho and Michigan are also holding nominating contests on Saturday to award delegates.

Trump has won every nominating contest so far by wide margins, putting him on track to have enough delegates to lock down the Republican presidential nomination by mid-March.

The victory portends trouble for Haley, who is the final candidate challenging Trump.

Republican presidential candidate Nikki Haley hosts a campaign event at Union Hall in Raleigh, North Carolina, on Saturday. Photo: Reuters

The former president won the first Michigan contest – a primary – on Tuesday by more than 40 percentage points.

For this election cycle, Michigan Republicans devised a hybrid nominating system, split between the primary and a caucus, which Trump easily won on Saturday.

Republicans were also holding caucuses in Idaho on Saturday, one of the final contests for Haley to alter the course of the race.

Attention will soon shift to Super Tuesday on March 5, when 15 states hold Republican nominating contests. Haley has vowed to stay in the race through then.

She has continued to campaign and raise funds over the past week in the wake of a crushing loss to Trump last Saturday in South Carolina, the state where she was governor twice.

Nikki Haley says Trump wants to use RNC as ‘piggy bank’ for his legal battles

Haley has argued that she should stay in the race despite the unlikely odds to give voters a choice beyond the former president.

She has made the case to voters that Trump’s legal challenges would distract him from the campaign, making him a less desirable candidate to challenge President Joe Biden.

Despite the losses, Haley has beat expectations set by polls in several of the early voting states.

She won more than 43 per cent of the vote in New Hampshire and nearly 40 per cent in her home state of South Carolina, both states where she spent significant time campaigning.

Adrian Robinson of St Louis, Missouri, sells merchandise before Donald Trump’s Get Out the Vote Rally and campaign event in Waterford Township, Michigan, in February. Photo: EPA-EFE

“There are huge numbers of voters in our Republican primaries who are saying they want an alternative,” Haley said last week.

Jai Chabria, a Republican strategist, said the latest win made clear that Haley had virtually no chance of clinching the nomination away from Trump.

“This race has been over for a long time since Donald Trump announced he was gonna become president,” Chabria said.

“There are a few in the donor class that wants us to go on, but that’s really it.”

Additional reporting by Reuters