“It bites,” he said. “For us, that’s huge money.”

And yet Mr. Harberts is standing by Mr. Trump.

He is on track to sell more parts than ever. He can’t hire fast enough to fill the geyser of orders coming in.

“If Hillary would’ve won, I don’t think we would’ve been in this mode,” he said. “In spite of the hassle and frustration, everyone is doing good.”

The question is how long those good times can last. Economists are certain that if the tariffs remain in place, they will lead to layoffs, farm foreclosures and bankruptcies — but not right away. Iowa may feel only a subtle effect by November, economists said, although any damage will almost certainly be felt in full by the time the state’s first-in-the-nation presidential caucuses roll around in early 2020.

“It’s possible that it might look good right up until the midterms,” said David Swenson, an economist at Iowa State University. “Even though everything we know about economics says that can’t be true in the long run.”

Already, there are signs that the tariffs are beginning to filter through the regional economy. Chinese buyers have been canceling hundreds of thousands of tons of soybean orders since April, according to Department of Agriculture data, and soybean prices fell close to a 10-year low in July. Soybean producers in Iowa stand to lose $624 million from the trade war, according to Chad Hart, an economist at Iowa State University.

In Iowa, trouble in the agriculture sector invariably spreads to the rest of the economy. Recent business surveys have found that farmers are becoming more reluctant to buy equipment and that local bankers are becoming gloomier in their outlook.