Joseph R. Biden Jr. on Thursday accused President Trump of “rooting for more violence” at a moment of national unrest over racism and police brutality, offering one of his most extensive responses yet to the Republican argument that he would be a weak leader on law enforcement and criminal justice.
After several days out of the spotlight during the Republican National Convention, Mr. Biden, the Democratic presidential nominee, spoke on MSNBC against a backdrop of upheaval in Kenosha, Wis., following the police shooting of a Black man, Jacob Blake, that outraged many Americans.
Some protests in Wisconsin have turned destructive, and Republicans have made clear that they sense a political opportunity, with Vice President Mike Pence declaring on Wednesday that “you won’t be safe in Joe Biden’s America.”
Mr. Biden, for his part, sought to turn the focus back to the coronavirus, and to cast the election as a choice between his promises of calm and Mr. Trump’s tendency to inflame already volatile situations that are developing under his presidency.
“He views this as a political benefit to him,” Mr. Biden said of the president. “He’s rooting for more violence, not less, and is clear about that. And what’s he doing? He’s kept pouring gasoline on the fire. This happens to be Donald Trump’s America.”
Mr. Biden was specifically referring to remarks earlier Thursday from Kellyanne Conway, Mr. Trump’s departing counselor, who said the president stood to benefit politically from the kind of unrest that has erupted in Kenosha.
“The more chaos and anarchy and vandalism and violence reigns, the better it is for the very clear choice on who’s best on public safety and law and order,” Ms. Conway said on “Fox & Friends.”
Mr. Biden, who noted that he condemned “violence in any form, whether it’s looting or whatever it is,” did not rule out a trip to Wisconsin himself, if a visit could be managed safely amid the pandemic.
“If I were president, I’d be going,” said Mr. Biden, who has spoken with Mr. Blake’s family. “If I went, what I’d be doing is trying to pull together the Black community as well as the white community, and sit down and talk, and talk about how we get through this.”
After Mr. Biden’s television appearances, his running mate, Senator Kamala Harris of California, delivered a speech in Washington in which she condemned the police shooting of Mr. Blake.
“It’s sickening to watch, it’s all too familiar and we must end it,” Ms. Harris said. She also said people should not travel to Kenosha with guns. An Illinois teenager was charged Wednesday with two counts of homicide after the fatal shootings of two people.
“We will not let vigilantes in our streets derail the fight for justice,” she said.
After her speech, Ms. Harris did not respond to shouted questions asking if she would travel to Kenosha.
All summer, Mr. Trump has deployed an onslaught of scattershot attacks against Mr. Biden, casting him by turns as too weak on crime and overly punitive. Up to this point, it hasn’t worked, and the president has trailed Mr. Biden in key battleground states amid strong disapproval of his stewardship during the coronavirus crisis.
Those competing Republican messages continued throughout Mr. Trump’s convention week, but as the unrest intensified in Wisconsin, so did Republican efforts to paint Mr. Biden — a relative moderate who does not want to defund the police — as an ally of the “radical left.”
“President Trump has repeatedly condemned the violence erupting in Democrat-led cities and has urged local Democrat leaders to accept federal support to stop the rioting,” said Tim Murtaugh, a spokesman for Mr. Trump, when asked about Mr. Biden’s claim that the president was “rooting” for violence.
The Wisconsin situation and attitudes about it are fluid. The white teenager who was arrested in the two killings in Kenosha appeared to support Mr. Trump and law enforcement on social media. The Justice Department has also announced a civil rights investigation into the police shooting.
But there are also early signs on the ground in that critical battleground state that the unrest has made Democrats more vulnerable, raising the stakes for Mr. Biden’s response headed into the fall campaign, with polls expected to tighten.
Also on Thursday, Speaker Nancy Pelosi of California said Mr. Biden should not debate the president, telling reporters that she believed her party’s nominee should not “dignify that conversation with Donald Trump.”
“I wouldn’t legitimize a conversation with him, nor a debate,” Ms. Pelosi said. She acknowledged that the Biden campaign felt differently, but said she considered Mr. Trump’s behavior during the 2016 debates against Hillary Clinton “disgraceful.”
A Biden campaign spokesman said in response that Mr. Biden would indeed debate Mr. Trump, a position that Mr. Biden himself affirmed on MSNBC. “I’m going to be a fact checker on the floor while I’m debating him,” Mr. Biden said, adding that Mr. Trump had a “somewhat pathological tendency not to tell the truth.”
Reporting was contributed by Emily Cochrane, Michael Cooper, Nicholas Fandos and Neil Vigdor.