“This is the end of his career,” said David Richter, a Republican businessman who has been campaigning for Mr. Van Drew’s seat since August and referred to him as a “weasel.”

Another Republican in the race, Brian Fitzherbert, who works for a defense contractor, was equally critical.

“He’s doing what he’s done for nearly 30 years,” he said. “Political survivorship. It’s desperation.”…

Mr. Richter added that any support Mr. Trump offered Mr. Van Drew, in exchange for the distraction a high-profile Democratic defection could offer in a week when the president faces impeachment, would quickly fade once Mr. Trump had “gotten what he wanted.”