The rally in Erie was another attempt to consolidate support in a state that was critical to the president’s success in 2016 but where he has struggled in polls against Mr. Biden.
Mr. Trump hammered his Democratic opponent’s energy policies, repeating a false claim that Mr. Biden supports a total ban on fracking, a major industry in the state.
In what Mr. Trump said was a first for one of his campaign rallies, he played on large video screens a montage of several clips in which Mr. Biden and his running mate, Senator Kamala Harris of California, talked about phasing out fossil fuels to combat climate change.
“If Biden is elected, he will wipe out your energy industry,” the president said.
Mr. Trump also offered a litany of false claims about Mr. Biden’s position on the coronavirus, saying that his opponent would “delay therapies, postpone the vaccine, prolong the pandemic.” He insisted that the United State was “rounding the turn on the pandemic,” even though the virus is surging around the country, including in Pennsylvania, where new cases over the past week have run 42 percent higher than the average two weeks earlier, according to a New York Times database — a level the state has not seen since April.
Mr. Trump had one other warning for voters there: that Mr. Biden, whom he calls “Sleepy Joe,” would fail to entertain them as he has. “If you want depression, doom and despair, vote for Sleepy Joe,” he said. “And boredom.”
Seeming to acknowledge his electoral deficit, the president pined for the days before the coronavirus when his electoral prospects looked at least somewhat brighter. Before “the plague” arrived, he said, “I wasn’t going to Erie. I mean, I have to be honest, there’s no way I was coming. I didn’t have to.”
Mr. Trump had been expected to be joined by the first lady, Melania Trump, for her first public appearance since she contracted the coronavirus.