Grand Rapids, Michigan - As expected, former President Donald Trump romped to victory in Michigan's Republican presidential primary, cementing his status as a shoo-in for the GOP's 2024 nomination.

Trump's rival Nikki Haley went down to a clear defeat, barely passing the 25% mark, while Trump boasted over 68% of votes with 99% of polling stations reporting.

Haley had already lost to Trump in the primaries in Iowa, New Hampshire, and South Carolina.

The race was called as early as Tuesday evening, and the sense that it was considered a foregone conclusion was bolstered by Trump's absence from the state.

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Instead, he called into a watch party and delivered a simple message: "We win Michigan, we win the whole thing."

Haley, the 77-year-old's last remaining challenger in the primaries, has previously promised to keep fighting as long as "a majority of Americans disapprove of both Trump and Biden." On Tuesday, she also restated her belief that Trump cannot win in November's election.

Some analysts, however, pointed out Trump's underperformance compared to the polls, with each victory so far coming in at a smaller margin than might have been expected. In fact, his victory was less convincing than that of President Joe Biden in the equivalent Democratic race.

The ex-president is currently embroiled in four criminal cases, as well as multiple civil trials – one of which resulted in a hugely damaging fraud verdict.

The Republican presidential primary could be officially wrapped up as soon as Super Tuesday on March 5, when voters in 15 states will pick their favorite candidate.