“What do you do if the Republican candidate is unpalatable to you?” asked Professor Holland, who also lives in the county. “Do you just show up and not vote for president at all? Or — gasp — could there be a possibility that a Republican woman would show up and vote for Hillary Clinton? We just don’t know.”

Delaware County was mostly farmland until a few decades ago, with a modest cluster of factories in the county seat. Roger Marksch, 67, built and fixed machines in those factories for almost 50 years before hanging up his tools last year. He watched as the factories closed or moved to Japan, China, Mexico and Finland. “I got out just in time,” he said with a laugh.

But even as those jobs faded away, developers were replacing Delaware’s soybean fields with subdivisions. Columbus was growing rapidly, fueled by a modern mix of government, education and financial services. Commuters doubled the suburban county’s population from 1980 to 2000, and it is on pace to double again by 2020, easily topping 200,000.

John Kasich, Ohio’s governor, is the archetypal local Republican with misgivings about Mr. Trump. Mr. Kasich, who lives in Delaware County’s southern tier, not far from a planned Ikea, has repeatedly rebutted Mr. Trump’s bleak descriptions of Ohio’s economy. He has not offered an endorsement.

Others said they were concerned Mr. Trump was insufficiently conservative. Craig Johnson, who owns a pizzeria in the county seat, said he doubted that Mr. Trump was a Republican, but he laughed when asked if he would consider Mrs. Clinton. “Listen, I’m a 45-year-old small-business owner in Delaware, Ohio, and I like guns, fishing and Nascar,” he said.

He is mulling a vote for Gary Johnson, the Libertarian nominee.

Many local Republicans are making their peace.