His main priority is voting for “the person who’s going to get more done” — that’s why he stuck with the Democrats in the midterms — but at the national level, he said, the Democrats have disappointed him on that front.

“ If you’re going to Washington, you need to do something,” he said. “If the only thing you’re going to do the whole time you’re there is try to get rid of the president, that’s a problem. I mean, Trump is not a great person, but you’ve got to get some work done.”

Other voters say they are preparing to take an even greater leap: vote for Mr. Trump after supporting Democratic congressional candidates in 2018 and Mrs. Clinton in 2016.

In the survey, 7 percent of those who supported Mrs. Clinton in 2016 said they now approved of the president’s performance — despite his personality and his Twitter account, many said.

“In 2016, I hated both” candidates, said Juli Anna California, 57, a nurse from Coral Springs, Fla. “I went with Hillary because Trump had no history as a politician.”

Mr. Trump has convinced her, though — not with his character, but with his policies.

“He’s not exactly the person I’d have as my best friend,” said Ms. California, who currently lives in Los Angeles as a traveling nurse. “But he’s a great president. Most politicians just talk about doing things, but Trump does them.”

Scott Will, 51, an equipment operator in Ligonier, Pa., also voted for Mrs. Clinton in 2016, and will vote for Mr. Trump next year. So will much of his family, union workers who had been “die-hard Democrats.” Mr. Will, who started college but left to get married before graduating, credits Mr. Trump’s trade deals and pledge to bring jobs back to the United States.