SCRANTON, Pa. — President Trump came to Joseph R. Biden Jr.’s hometown on Thursday and said he was prepared to run against the former Democratic vice president in November, changing gears after being “mentally” ready to take on Senator Bernie Sanders of Vermont.
“I was all set for Bernie because I thought it was going to happen,” he said. “And then we have this crazy thing that happened, right?”
Mr. Trump, speaking at a televised town hall event hosted by Fox News, was referring to Mr. Biden’s unexpected resurgence in the Democratic primaries on Tuesday, just as his campaign seemed at risk of collapsing.
In a venue where two Trump supporters questioned whether the president’s slash-and-burn tone was necessary, Mr. Trump, 73, ridiculed Mr. Biden, 77, for a series of recent gaffes and insinuated that his rival’s mental acuity was slipping.
The president referred to the votes “on Tuesday, which he thought was Thursday” — a reference to Mr. Biden’s use of the erroneous phrase “Super Thursday.” Mr. Trump also mocked his potential November rival for mistakenly saying in late February that he was “running for Senate” and for wildly overstating the number of gun deaths in the United States.
“There’s something going on there,” Mr. Trump said, to laughter from the crowd of a few hundred local supporters.
The setting, in which he took questions from the audience prescreened by Fox News, was an unusual one for the president, who regularly delivers hour-plus monologues before thousands at campaign rallies in large arenas. His quiet exchanges with polite questioners was a far cry from the shouted slogans and bawdy call-and-response of his typical “Keep America Great” events.
In a city chosen by the White House, the event was part of a series that Fox News has staged with several Democratic candidates, including Mr. Sanders, who continues to battle Mr. Biden for the Democratic presidential nomination.
Mr. Trump said he had prepared his attacks on Mr. Sanders. “So, mentally, I’m all set for Bernie — communist, I had everything down, I was all set,” he said.
One Trump supporter told the president that he was concerned about nasty messaging in American politics, while another said her family members would not speak to her because of her support for him. She asked Mr. Trump how he would unite the country.
In each case, the president blamed his opponents for incivility. “When they hit us, we have to hit back,” he said. “I wouldn’t be sitting up here if I turned my cheek.”
Mr. Trump defended his handling of the spreading coronavirus, and deflected a question about why he did not act sooner to change Obama-era regulations that he has blamed for delaying testing kits. He said he was “thinking about a lot of other things, too, like trade and millions of other things.”
“As soon as we found out it was a problem,” he added, “we did it.”
Asked whether he would stop shaking hands because of the outbreak, Mr. Trump, a self-described germophobe who has said he envies the Japanese custom of bowing, called it a practical impossibility.
“I love the people of this country, and you can’t be a politician and not shake hands,” the president said. He cast aside the advice of public health officials who have urged Americans to avoid contact, which can spread the coronavirus.
“Now the concept of shaking hands since this — you’re hearing a lot of stuff about trying not to shake hands, and that has not stopped me at all,” he said.
After the event, Mr. Trump stayed for several minutes and shook dozens of hands with no evident distress.
The president’s hourlong appearance, moderated by the Fox News hosts Bret Baier and Martha MacCallum, was peppered with factual inaccuracies and misleading statements.
Reminded by Mr. Baier that he has presided over a flood of red ink, Mr. Trump insisted that he cared about the national debt and would make tackling it a priority in a second term.
As a candidate, Mr. Trump once boasted that in eight years he would eliminate not just the annual deficit but the entire national debt. Instead, the debt has increased by about $3.5 trillion since he took office, despite a healthy economy. The president attributed that largely to his spending increases on the military, disregarding his tax cuts or domestic spending increases.
His insistence contradicted his own acting chief of staff, Mick Mulvaney, who told an audience last month in Britain that Republicans cared about the deficit when a Democrat was president. “Then Donald Trump became president, and we’re a lot less interested as a party,” Mr. Mulvaney said.
Mr. Trump repeated a claim that President Barack Obama tried to meet with North Korea’s leader, Kim Jong-un, only to be rebuffed, an unsubstantiated assertion that he has previously aired and that seems to have been pulled out of thin air. The president said that he maintained a “good relationship” with Mr. Kim, though he did not claim new progress toward coaxing the North’s leader to relinquish his nuclear program.
The president also falsely claimed that Scranton now has “the lowest and best unemployment numbers” ever. Its unemployment rate for April 2019, 4 percent, was the lowest since 1990, the earliest year for which data is available. But the rate has since increased to 5.6 percent in December, which was higher than the 5.4 percent recorded in December 2016.
Mr. Trump appears regularly on Fox News, but despite coverage that heavily favors him over all, he has also expressed irritation with the network for occasional critical segments and unfavorable polling.
Last week, after a survey conducted by the network showed five Democratic candidates defeating Mr. Trump in head-to-head matchups, the president lashed out in frustration.
“Why doesn’t Fox finally get a competent Polling Company?” Mr. Trump posted on Twitter.
He also groused about the network on Monday at a rally in Charlotte, N.C.
“They want to be politically correct,” he said, adding, “I don’t know what’s going on with Fox.”
Mr. Trump narrowly carried Pennsylvania in 2016, by 44,000 votes. He said he would “win it again very easily,” but recent polling in the state has shown him tied with or trailing both Mr. Biden and Mr. Sanders.
Mr. Biden, who now lives in Wilmington, Del., takes great pride in his roots in Scranton, a working-class city of 76,000 in northeastern Pennsylvania.
“Everything my sister, Valerie, and I learned was in Scranton,” he said during an appearance in October at the same venue, the Scranton Cultural Center. “Scranton creeps into your heart and never leaves you.”
Peter Baker and Linda Qiu contributed from Washington.