YOUNGSTOWN, Ohio — In May 2016, David Betras, a Democratic Party leader in the heart of industrial northeast Ohio, sent a memo warning Hillary Clinton’s campaign that it was on the verge of losing Ohio, Pennsylvania and Michigan because she was not connecting with blue-collar voters. These states “should be easy wins for us,’’ he wrote.

He said he got no answer. As he sees it now, Democrats are still just as out of touch.

Mr. Betras, who recently stepped down as Democratic chairman of populous Mahoning County, said that while Democrats in Washington harp on President Trump’s unfitness for office, his taxes and possible impeachment, the president is solidifying blue-collar support through an aggressive trade war with China, even if his tariffs mean economic pain in the short term.

“The Democratic Party has lost its voice to speak to people that shower after work and not before work,” he said. “All we’re saying is he won’t turn over his tax returns. He’s saying, ‘I’m fighting China to get you better jobs.’”

He added: “They don’t care about his taxes — they just don’t.’’

In the 10th year of a national recovery, which has brought record low unemployment and rising wages to many parts of the country, northeast Ohio is still among the walking wounded, the result of decades of deindustrialization driven by free trade deals. The loss of 1,600 jobs in March at a General Motors plant in nearby Lordstown, despite Mr. Trump’s visible efforts to save them, was the latest blow.