There are other reasons Republicans might prevail in Iowa. The unemployment rate is among the lowest in the country, and jobs are abundant. Immigration has become a thorny issue after Republicans seized on the death of an Iowa college student — authorities say she was killed by an undocumented immigrant — as evidence the country needed more secure borders. More recently, the bitter fight over Justice Brett M. Kavanaugh’s confirmation has outraged many Republican voters.

“A lot of us are disgusted with what the Democrats have been doing,” said Joleen Ballard, 66, who was selling pumpkins and gourds at a fall festival in Toledo, a small town about 70 miles from Des Moines. She voted for Mr. Trump, she said. And come Election Day, she planned to vote for Ms. Reynolds.

“She’s been through what a lot of us in Iowa have,” Ms. Ballard said. “She’s one of us.”

Mr. Trump’s success among white, working-class voters spanned much of the Midwest, powering victories in Michigan, Wisconsin and Ohio. As Democrats try to reclaim these states, they are counting on young voters, women and minorities in the cities and suburbs to provide the bulk of Democratic support. But here in Iowa and elsewhere, they are also making appeals to small-town voters who went for Mr. Trump.

It was no coincidence, for example, that Mr. Hubbell chose as his running mate Rita Hart, a farmer and state senator who represents rural areas in the eastern part of the state.

Mr. Hubbell, whose family name is so entrenched in Des Moines that one of the main roads leading out of the city is called Hubbell Avenue, likes to talk about how he is a fifth-generation Iowan. He is banking heavily on a moderate, Iowa-focused message that revolves around “bread-and-butter issues” — health care, education, the economy.

He tends to pepper his remarks with financially abstruse phrases like “fiscal impact analysis” and “tax-credit review panel.” He rarely, if ever, mentions Mr. Trump. “I got to be honest with you,” he said, “I’m pretty well focused on what’s going on in our state.”