Ben Ingebretson was a reliable Republican voter. A Christian minister who works for a faith-based nonprofit, Mr. Ingebretson said he shared Republicans’ small-government views and agreed with the party’s calls for fiscal conservatism.

But after Donald J. Trump became the face of the party, Mr. Ingebretson, who lives in Grand Rapids, Mich., drifted away from his political roots. In 2020, he voted for President Biden. And in February, he was among the 34 percent of voters in his county who cast ballots for Nikki Haley in the Republican primary, even though her presidential campaign seemed doomed before the Michigan election.

With a Trump-Biden rematch locked in for November, Mr. Ingebretson, 66, expects to vote again for Mr. Biden, though he grades the incumbent’s job performance as just a C. He said he approved of Mr. Biden’s vision for America as “a beacon” in the world, but not his student loan forgiveness and pandemic-era stimulus spending.

“I have far greater confidence in Biden to lead from a posture of character,” Mr. Ingebretson said, though he added, “I wish both parties were bringing better persons to the table.”

The political transformation, and exasperation, of Mr. Ingebretson is not unique in the Grand Rapids area, a longtime Republican stronghold that has shifted toward Democrats. Kent County, which includes Grand Rapids on the western side of Michigan, helped Mr. Trump narrowly win the state in 2016, and helped flip the state to Mr. Biden four years later.