But in the poll a substantial chunk of Mr. Biden’s voters did not express an actively positive view of their candidate. Forty-two percent of likely voters expressed a favorable view of him, and 42 percent unfavorable.
The poll is an outlier in this regard, as a number of other high-quality Pennsylvania polls in recent weeks, including one from The New York Times and Siena College, have shown Mr. Biden’s favorability reaching or surpassing 50 percent. But as recently as mid-September, most of those same polling firms had shown less than half of voters expressing a favorable view of Mr. Biden.
Christopher P. Borick, a political science professor at Muhlenberg who runs its polling institute, said that these results brought back shades of 2016, when both candidates were widely disliked but Mr. Trump succeeded in convincing swing voters that Mrs. Clinton was the worse option. “It’s no surprise, when you look at the president’s campaign and his efforts to drag Biden down, that he thinks that’s the path again,†Dr. Borick said.
The key difference is that Mr. Biden has not faced the same antipathy as Mrs. Clinton, who was disliked by an equal share of Pennsylvania voters as Mr. Trump was. The president’s attempts to drive up negative opinions of Mr. Biden — including his misleading accusation that, if elected, the former vice president will ban fracking in Pennsylvania — have so far not succeeded.
In 2018, Democrats picked up four House seats in Pennsylvania, largely in suburban areas, and Mr. Trump is struggling in those regions. Mr. Biden has made them a primary focus, as he did on Saturday, when he spoke in Dallas Township, a suburb of Wilkes-Barre, hammering Mr. Trump for his handling of the coronavirus crisis.
But polls show that Mr. Biden has yet to fully capitalize on the softening of Mr. Trump’s support. Averaging the results of the most recent Times/Siena and Morning Call/Muhlenberg polls, in the Philadelphia suburbs Mr. Trump is polling nine points behind the share he received there in 2016 exit polls, but Mr. Biden is only three points ahead of Mrs. Clinton’s total among this group.
Troubling for Mr. Biden in a different way is the fact that he has not yet matched Mrs. Clinton’s share of support in Philadelphia proper. Averaging the results of the two recent polls, he has the backing of 73 percent of Philadelphia voters, down from 83 percent for Mrs. Clinton in 2016. According to the Times/Siena poll, Mr. Trump was supported by 24 percent of Philadelphians, nine points ahead of his exit poll numbers in 2016.
