WILMINGTON, Del. (AP) — Joe Biden and Kamala Harris pushed past their one-time political rivalry Wednesday to deliver an aggressive attack on the character and performance of President Donald Trump in their historic first appearance as running mates.

The physical debut of the Democratic ticket was without parallel in recent political annals. The coronavirus prevented Biden and Harris from appearing before the large, adoring crowd that typically greets a presidential nominee and his or her running mate. Instead, they spoke in a mostly empty high school gym where reporters nearly outnumbered campaign aides and the candidates’ family members.

While the pandemic made a traditional campaign rollout impossible, it gave Biden and Harris a setting to emphasize their criticism of Trump as unable to contend with the most severe public health crisis in a century. Harris was particularly sharp in her condemnation of the administration.

“The case against Donald Trump and Mike Pence is open and shut,” Harris said. “This virus has impacted almost every country. But there’s a reason it has hit America worse than any other advanced nation. It’s because of Trump’s failure to take it seriously from the start.”

She added: “This is what happens when we elect a guy who just isn’t up for the job.”

Harris is the first Black woman on a major party’s presidential ticket, and she and Biden noted the historical significance.

“This morning, all across the nation, little girls woke up — especially little black and brown girls, who so often feel overlooked and undervalued in their communities. But today, today, just maybe, they’re seeing themselves for the first time in a new way,” Biden said.

Harris, who is also of South Asian descent, noted the “heroic and ambitious women before me, whose sacrifice, determination and resilience make my presence here today even possible.”

For his part, Trump has struggled to land on a coherent message about the Biden-Harris ticket, casting the Democrats as simultaneously too liberal for America and yet not progressive enough for their party’s base. Trump has resorted to sexist and racist criticism, referring to Harris as “nasty” and tweeting that “the ‘suburban housewife’ will be voting for me” to keep neighborhoods safe.

He also noted the two Democrats’ disagreements during the primary campaign last year.

“She said horrible things about him,” Trump said Wednesday. “She mocked him, openly mocked him. That’s why I thought that was a very risky pick. Because I’m sure that will be played back.”

But onstage in Wilmington, Biden and Harris showed clear affection toward one another. He called his running mate an “honorary Biden,” and Harris offered a poignant tribute to his son Beau, whom she was friends with when both served as state attorneys general. Biden seemed overcome with emotion as Harris spoke of Beau, who died in 2015, as “the best of us” and a man who modeled himself after his father.

She signaled that she’ll offer a vigorous defense of Biden’s qualifications on issues of race and civil rights, though she made headlines for assailing him for his past opposition to federally mandated busing during a primary debate.

Noting Biden’s own vice presidency under President Barack Obama, she said he “takes his place in the ongoing story of America’s march towards equality and justice” as the only person “who’s served alongside the first Black president.”