The governor’s race could be further complicated by the candidacy of Mayor Mike Duggan of Detroit, a longtime Democrat who announced last year that he would run as an independent, an effort to distance himself from the Democratic Party brand after Mr. Trump flipped the state back to the Republican column in the presidential race last November.

John James on Monday launched a bid for Michigan governor, forgoing a re-election campaign to his House seat in a swing district. The two-term representative and ally of President Donald Trump said in his announcement on social media that he felt compelled to run because Michigan is “being held back by the lack of strong,