Former President Donald J. Trump won Michigan’s Republican presidential primary election on Tuesday, moving closer to a general election rematch against President Biden.

Mr. Biden easily won his own primary, though he faced a groundswell of opposition from voters who are protesting his staunch support for Israel and its military campaign in Gaza by casting ballots not for another candidate, but for “uncommitted.” The Associated Press called both contests as soon as final polls closed at 9 p.m. Eastern time.

Mr. Trump’s victory over Nikki Haley, the former governor of South Carolina, extends an unbroken streak in the nominating contests. Michigan is his sixth straight triumph, and it is his second, after Nevada, in a state expected to be a crucial battleground come November.

“We win Michigan, we win the whole thing,” Mr. Trump told supporters at the Michigan G.O.P. watch party over the phone after the race was called, according to a transcript of the call provided by his campaign. He added that Tuesday’s results were “far greater than anticipated.”