Also working in their favor: Far fewer voters are undecided this year, lowering the likelihood of a late break in one direction or the other.
The trend in Michigan toward Democrats over the past four years has been driven largely by white women and college-educated voters, as it has been nationwide. The phenomenon has been most visible in the suburbs just north of Detroit and Ann Arbor, where the pollster Stanley Greenberg first coined the term “Reagan Democrats” in the 1980s to describe the moderates who were flipping in large numbers to support Ronald Reagan.
Since then, much of the region has been solidly Republican. But the insurgent Democratic candidates Elissa Slotkin and Haley Stevens both won decisive victories in 2018 House elections there, turning their districts blue.
“The changes in Oakland County have been shocking,” Mr. Czuba said, referring to a suburban county that runs through both Ms. Slotkin’s and Ms. Stevens’s districts. “Oakland County used to be the breadbasket of the Republican Party. In the 1980s, Democrats would not have even considered winning Oakland County. But now we’re in a position where Oakland County has become a blood bath for the Republican Party.”
Mr. Trump has also been leaking support in the western part of the state, long a Republican stronghold, and home to a heavily religious Protestant electorate. Two years ago in the governor’s race, Gretchen Whitmer won populous Kent County, which includes Grand Rapids, a typically Republican area in Western Michigan that had voted for Mr. Trump. Representative Fred Upton, a Republican representing the southwestern corner of the state, won re-election by less than five points in 2018, the narrowest margin of his career.
The pollster Bernie Porn, whose firm, EPIC-MRA, conducts surveys on behalf of The Detroit Free Press, said that it had found that respondents in Western Michigan registered a drop in approval for Mr. Trump after his photo op in front of St. John’s Church in Washington. But he added that Mr. Trump’s recent emphasis on crime and safety had resonated there in ways it didn’t elsewhere, helping the president recover some support in the most recent Free Press poll.
“Some of the messaging that Trump is using in terms of crime in the cities — that is starting to take effect,” Mr. Porn said.