North of Dimondale, Clinton County offers another example. Mr. Trump won the county, but it has experienced a loss of more than a quarter of its manufacturing jobs.
In Pennsylvania, the losses were not as steep but two counties that Mr. Trump won easily, Wyoming and Warren, had the highest percentage declines in the state. The same was true for Trempealeau and Rusk Counties in Wisconsin, where a Democrat, Tony Evers, ousted the incumbent Republican governor, Scott Walker, a strong supporter of the president, in 2018.
These are the kind of places about which President Trump should feel most confident in 2020. But their shifting economic fortune could now test how far his appeal to white working-class voters stretches and whether their cultural alliance with him is enough to persuade them to stick with him.
Judd Deere, a White House spokesman, pushed back at the idea of manufacturing job losses in Michigan, Wisconsin and Pennsylvania.
“President Trump has a vision of ensuring policies are in place that support a growing economy and the American worker, including our great manufacturers,” he said in a statement. “The president has not only lowered taxes for hard-working families, his leadership and passage of the Tax Cuts and Jobs Act along with deregulation has led to an unprecedented period of job and wage growth across the country, and Michigan, Pennsylvania and Wisconsin are no exceptions.”
But the president faces troubling poll results in all three states.
A poll published this month in The Detroit Free Press and conducted by the Lansing-based polling firm EPIC-MRA, showed that only 32 percent of voters surveyed would vote for Mr. Trump’s re-election, a finding consistent with the company’s poll in March. It also found that former Vice President Joseph R. Biden Jr., who is running for the Democratic nomination, led Mr. Trump by 11 points.
“That’s a guy in trouble,” said Bernie Porn, the president of the polling firm. “Those numbers are really indicative of someone who is going to have problems.”