WASHINGTON (AP) — While Joe Biden and Donald Trump are marching steadily toward their respective presidential nominations, Michigan's primary on Tuesday could reveal significant political perils for both of them.

Trump, despite his undoubted dominance of the Republican contests this year, is facing a bloc of stubbornly persistent GOP voters who favor his lone remaining rival, former U.N. Ambassador Nikki Haley, and who are skeptical at best about the former president's prospects in a rematch against Biden.

As for the incumbent president, Biden is confronting perhaps his most potent electoral obstacle yet: an energized movement of disillusioned voters upset with his handling of the war in Gaza and a relationship with Israeli Prime Minister Benjamin Netanyahu that critics say has been too supportive. (

Those dynamics will be put to the test in Michigan, the last major primary state before Super Tuesday and a critical swing state in November's general election. Even if they post dominant victories as expected on Tuesday, both campaigns will be looking at the margins for signs of weakness in a state that went for Biden by just 3 percentage points last time.

(Thumbnail image: A vote sign and American flag outside a Michigan primary election location in Dearborn, Mich., Tuesday. AP Photo/Paul Sancya)