The presidential contest took another acrimonious turn on Thursday as Joseph R. Biden Jr.’s campaign amplified its denunciations of President Trump over revelations that he had knowingly minimized the risks of the coronavirus, and the Trump campaign tried to deflect blame back onto Mr. Biden.
A day after book excerpts and audio recordings showed that Mr. Trump had privately acknowledged to the journalist Bob Woodward early this year that he knew of the virus’s danger but downplayed it anyway, Biden surrogates vigorously denounced the president’s response to the public health crisis, directly linking it to the loss of American lives.
The Trump campaign, on the defensive for the second day over Mr. Trump’s faltering pandemic response, attempted to control the fallout from the Woodward book by striking back at Mr. Biden for what it claimed was the former vice president’s “behind the curve” handling of the virus.
The condemnations from the Biden campaign continued in the afternoon, when the vice-presidential candidate, Kamala Harris, also accused the president of recklessly endangering American lives.
“He had all this information yet he held rallies, he suggested that to wear a mask is a sign of weakness as opposed to a sign of strength,’’ Ms. Harris said at an appearance in Florida. “This is the president of the United States. So we continue to have examples of the fact that this is an individual who is not concerned about the health and safety and well-being of the American people and is frankly engaged in a reckless disregard for the lives and health and well being of the people of our country. I find it so outrageous.”
The dueling attacks over the virus signaled a new, increasingly bitter front in the presidential campaign and heralded the extent of the ugliness that will likely come as both men seek to shore up support with less than eight weeks to go until the general election on Nov. 3.
The urgency of the attacks also underscores how detrimental Mr. Trump’s failure to contain the pandemic has been for his re-election prospects. A majority of voters continue to disapprove of the way Mr. Trump has handled the pandemic: In a Monmouth University poll released this week, only 37 percent of registered voters said the president had done a good job handling the virus, while 56 percent said he had done a bad job.
Sensing a potent political opportunity, Mr. Biden and his surrogates have aggressively seized on Mr. Trump’s remarks to Mr. Woodward. Though Mr. Biden had planned on Wednesday to take on Mr. Trump over the economy and protecting American jobs during an appearance in Warren, Mich., he quickly pivoted to lace into Mr. Trump over the revelations in Mr. Woodward’s book about his handling of the virus, denouncing the president’s response as “beyond despicable.”
“He knew how dangerous it was,” Mr. Biden said. “And while this deadly disease ripped through our nation, he failed to do his job on purpose. It was a life-and-death betrayal of the American people.”
On Thursday surrogates for Mr. Biden offered a stinging rebuke of the president during a call with reporters, repeatedly stressing that Mr. Trump had lied to Americans about the threat of the virus.
“My dad trusted the president,” said Kristin Urquiza, whose 65-year-old father died of the virus in Arizona in June, not long after the state lifted many stay-at-home restrictions. “He listened to the president and followed his advice,” she continued, echoing remarks she made at the Democratic convention last month.
“And sure, my dad did not panic. But instead, he died.”
Senator Sherrod Brown, Democrat of Ohio, who was also on the call, said Mr. Trump’s decision to play down the virus was “the definition of Donald Trump’s phony populism.”
“He sold the American people these lies, then he betrayed them and people died,” Mr. Brown said.
Mr. Trump’s private admission that he had intentionally played down the deadliness of the coronavirus burst into the open on Wednesday, after several news outlets obtained advance copies of Mr. Woodward’s book “Rage.” The book revealed that Mr. Trump had known as early as February that the coronavirus was more dangerous than the flu even as he told the country otherwise.
“I wanted to always play it down,” the president said in a tape-recorded interview with Mr. Woodward on March 19.
When pressed by reporters on Wednesday about why he did not do more in February and March, given what he knew, Mr. Trump said that he had not expected the virus to spread as far and as fast as it did.
“You didn’t really think it was going to be to the point that it was,” he said. “All of a sudden the world was infected. The entire world was infected. Everyone was scrambling around looking where to buy face masks and all of the other things.”
Mr. Trump was scheduled to hold an afternoon news conference at the White House on Thursday and travel to Freeland, Mich., for an evening rally. Mr. Biden had no public events scheduled.
In a memo to reporters, the Trump campaign pointed to the Biden campaign’s decision to hold an indoor rally in Michigan in early March — while ignoring that Mr. Trump had continued to hold rallies even as he was aware that the virus was deadly, and that he held an indoor rally in Oklahoma in June after more than 100,000 people had died in the United States.
“While President Trump was already taking decisive action to protect the country in the early months, Biden was saying barely anything about the pandemic and continuing about his campaign as normal,” the Trump campaign said.
Attempting to parry the Trump campaign’s attacks, Bill Russo, the deputy communications director for the Biden campaign, laid out steps Mr. Biden took as the outbreak grew, including an op-ed article Mr. Biden wrote about the dangers of the virus in January.
Asked by a reporter about the campaign’s decision to hold an indoor rally on March 9, on the eve of the Michigan primary, before the virus had upended traditional campaigning, Mr. Russo acknowledged that the rally, in retrospect, may have been a mistake but tried to shift the focus back to Mr. Trump.
“Maybe those are decisions that, you know, that look a little bit differently in hindsight,” Mr. Russo said. “But maybe if the president of the United States hadn’t been lying about the extent of the crisis that we were facing, we would have had different information to make different decisions.”