But among both subgroups, Mr. Trump lagged his 2016 benchmarks. He led with white voters without four-year degrees by 14 points; in 2016, he won these voters by 32 points, according to exit polls. Among rural voters, he held a 26-point lead; four years ago he won rural Pennsylvania voters by 37 points.
The first presidential debate on Tuesday night gives Mr. Trump an opportunity to shake up the race, and the poll suggested some Biden supporters are in a defensive crouch. Voters were closely divided on whom they expected to win the debate: 39 percent named Mr. Biden and 41 percent said Mr. Trump. Nearly three out of four voters who identified as Democrats expected a Biden win, with 9 percent expecting Mr. Trump to prevail and 17 percent unsure. Voters who identify as Republicans are slightly more confident that Mr. Trump will win.
“I’m nervous that Biden will fumble words or not be clear and get attacked, because Trump is a bully and Biden is not,” said Maryann Lemerise, 55, a Philadelphian who has rearranged her work schedule to make phone calls for Mr. Biden.
Laura Gallagher, 59, a pharmacy worker in the Lehigh Valley who is a strong Trump supporter, is looking forward to the debate. “I think it’s going to be a joke,” she said, “because I don’t think the Democratic candidate is going to be able to do it. I don’t think he has it in him.”
A third voter, Michael Sullivan, 54, who cast a ballot for the Green Party in 2016, is undecided and is looking to the debate to settle his choice. He said he would decide based on how the candidates handle themselves.
Mr. Biden is “like your grandfather, that you’re worried he’ll hurt himself if you don’t take his license away,” he said. He wants to hear Mr. Trump respond to questions with a “valid answer, not a deflection,” adding, “Then I might think of voting for him.”