Donald Trump has won Michigan’s Republican primary election, the latest in a string of convincing primary victories as he closes in on the GOP presidential nomination.

The Associated Press called the race for Trump over the former South Carolina governor Nikki Haley at 9pm ET.

The former president has repeatedly trounced Haley in the primaries, but she has hung on with a campaign that continues to highlight areas of weakness for Trump and offers Republicans uneasy about Trump a protest vote of their own. Haley has pledged to stay in the primaries at least through next Tuesday, 5 March, when 15 states will vote and Trump could all but sew up the Republican nomination.

But there are some warning signs for Trump in his easy victory. His commanding lead was weaker in Oakland county, a traditionally Republican area with a large number of college-educated voters.

Speaking at a press conference in Grand Rapids ahead of the primary, Haley argued that the bloc of Republicans who have continued to turn out for her despite Trump’s dominance in the primaries signaled trouble for Trump in November.

“You can’t win a general election if you don’t acknowledge the 40% of Republicans who are saying we don’t want Donald Trump,” said Haley, referring to the share of Republican voters in South Carolina who voted for her.

This primary only decided about 30% of Republican delegates from Michigan – because of a scheduling change, to stay in compliance with Republican National Committee rules, most delegates will be assigned during the state’s Republican convention and caucus on Saturday.