Coronavirus meant the debut of the Democratic ticket was held without an adoring crowd, with the pair speaking in a high school gym where reporters outnumbered aides.
While the pandemic made a traditional campaign roll-out impossible, it gave Mr Biden and Ms Harris a setting to emphasise their criticism of Mr Trump as unable to contend with the most severe public health crisis in a century.
Ms Harris was particularly sharp in her condemnation of the administration.
She said: “The case against Donald Trump and Mike Pence is open and shut.
“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.
“This is what happens when we elect a guy who just isn’t up for the job.”
Let's get to work, @KamalaHarris. pic.twitter.com/EjtUpgaieI
— Joe Biden (@JoeBiden) August 12, 2020
Ms Harris is the first black woman on a major party’s presidential ticket, and she and Mr Biden noted the historical significance.
Mr Biden, former vice president to Barack Obama, said: “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.”
Ms 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, Mr 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.
Mr Trump has resorted to sexist and racist criticism, referring to Ms Harris as “nasty” and tweeting that “the ‘suburban housewife’ will be voting for me” to keep neighbourhoods safe.
He also noted the two Democrats’ disagreements during the primary campaign last year.
“She said horrible things about him,” Mr Trump said on 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, Mr Biden and Ms Harris showed clear affection toward one another.
He called his running mate an “honorary Biden”, and Ms Harris offered a poignant tribute to his son Beau, whom she was friends with when both served as state attorneys general.
Mr Biden’s choice of Ms Harris brought more than just historical weight to the ticket — it also provided a big fundraising boost for the campaign.
He announced at a later online fundraiser that the campaign raised 26 million dollars (£20 million) in the 24 hours since she was announced, with 150,000 people giving for the first time.
