Michigan Threatens to Slip From Trump as He Goes Quiet on Airwaves

“Particularly women in the suburbs broke in a big way for us Democrats,” said Mr. Gilchrist, who was elected with Ms. Whitmer, “and I think the Biden campaign is running an effort to continue to build on that momentum.”

Then there are Mr. Trump’s self-inflicted political wounds in the state, none more public than his insults of Ms. Whitmer as she locked down the state after the virus began spreading in March, calling her “half Whitmer” and “the woman in Michigan.”

Ms. Whitmer was one of a series of Michigan women whom the president has belittled: the attorney general, the secretary of state, the chief executive of General Motors and two members of Congress.

“I don’t know any other state where he’s gone after as many women,” Ms. Dingell said. Mr. Trump also mocked her late husband, former Representative John D. Dingell, at a rally last year, suggesting he had gone to hell and was “looking up.”

Three state polls last week showed Mr. Biden winning female voters by wide margins, from 15 to 29 percentage points, and ahead in the state over all by six to 12 points.

Mr. Biden is seen as a stronger candidate in Michigan than Mrs. Clinton was, especially after he swept all 83 counties in the Democratic primary race against Senator Bernie Sanders of Vermont. Four years earlier, Mr. Sanders carried 73 counties against Mrs. Clinton, and some of his strongest areas were rural and white regions that would go on to vote overwhelming for Mr. Trump in the fall.

Mr. Trump carried non-college-educated white voters in Michigan by more than 30 percentage points, according to 2016 general election exit polling. Last week, separate CNN and Fox News polls of the state showed that Mr. Trump’s lead among that group had shrunk to only 10 points.