Democrats Mr Biden and Ms Harris used their debut as running mates to unify against President Trump. The former prosecutor, Ms Harris, compared Mr Trump’s handling of the pandemic with Mr Obama’s and Mr Biden’s management of the much smaller Ebola outbreak in 2014.
Ms Harris said: “That is what’s called leadership.
“But compare that to the moment we find ourselves in now.”
She added: “As somebody who has presented my fair share of arguments in court, the case against Donald Trump and Mike Pence is open and shut.”
Mr Biden accused Mr Trump of “whining” about the appointment of his new running mate.
He said: “Donald Trump has already started his attacks, calling Kamala ‘nasty’, whining about how she is ‘mean’ to his appointees.
“It’s not a surprise because whining is what Donald Trump does best, better than any president in American history.
“Is anybody surprised that Donald Trump has a problem with a strong woman, or strong women across the board?”
The pair’s appearance in Wilmington, Delaware, gave a glimpse into how Mr Biden and Ms Harris will battle Mr Trump in the presidential election.
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She said Mr Trump “inherited the longest economic expansion in history, from Barack Obama and Joe Biden.
“And then, like everything else he inherited, he ran it straight into the ground.”
“This is what happens when we elect a guy who just isn’t up to the job – our country ends up in tatters, and so does our reputation around the world.”
Ms Harris added: “America is crying out for leadership, yet we have a president who cares more about himself than the people who elected him.”
Mr Biden also highlighted how Ms Harris is the first woman of colour to serve as a presidential running mate for a major US party.
He added: “The choice we make this November is going to decide the future of America for a very, very long time.”
Mr Biden will formally accept the Democratic presidential nomination at next week’s party convention.
Mr Trump is set to be nominated for a second term in the White House by the Republicans a week later.
Americans will choose their president on 3 November after the two candidates battle for votes.
Mr Trump’s running mate is Vice-President Mike Pence.