Representative Nancy Pelosi, the minority leader, and other top Democrats advised the party’s candidates this week, in a memo and a conference call, to speak not of impeachment, but of a “culture of corruption” under Mr. Trump, for which a Democratic House would be a check.

The president weighed in that his removal from office would cause the booming stock market to crash and make Americans “very poor.” Whether he was consciously trying to motivate his supporters in the midterms was unclear. “I don’t know how you can impeach somebody who’s done a great job,’’ he added.

The campaign of Mark Harris, the Republican House candidate in the Ninth District, suggested it is eager to bring up the subject, as a prod to the Republican base. For now, though, the threat of impeachment seems not to have broken through to many voters yet. The race here is competitive largely because many of the president’s voters are complacent, while Democratic supporters are angry and eager to turn out.

Sheila Moysakis, 54, a beauty salon owner in Unionville, who called herself a strong Trump supporter, said Mr. Trump’s payments to a porn star and a Playboy model ahead of the 2016 election did not concern her. “That kind of stuff doesn’t normally blow my skirt up,” she said.