It could also be temporary if, as some in the industry think, the problem is related to excess inventory, he said. Still, the health of the industry, which has a track record as an economic bellwether, bears watching. “R.V.s have always preceded the rest of the economy in a downturn and in an upturn,” Mr. Curtin said.

Frank Hugelmeyer, the R.V. association’s president, declined to comment.

The impact of the president’s tariffs on everything from steel to soybeans is playing out against the backdrop of the midterm elections, with some Republicans trying to make a robust economy central to their case for maintaining control of Congress. In Indiana, Missouri, North Dakota and other states, the president’s policies are starting to be felt, especially in industries that have large trading relationships with China.

“I think there’s serious concern about the effects of tariffs on the R.V. industry,” said Senator Joe Donnelly, Democrat of Indiana and one of the Senate’s most vulnerable incumbents this year. His home is nearby. “So many of the components that go into R.V.s are directly affected by these tariffs.”

“It is something that we watch very, very closely having gone through the other side of this when unemployment was 22 percent,” Mr. Donnelly said, referring to the unemployment rate in Elkhart at the peak of the Great Recession.