The US president had, hours earlier, called Kamala Harris “nasty” after she became the first Black and South Asian woman to appear on a mainstream party’s presidential ticket.
His attacks against both Mr Biden and Ms Harris come despite Mr Trump having donated to the Democratic vice presidential candidate’s bids to become California’s attorney general between 2011 and 2013.
Following the former vice president's event formally announcing his running mate on Wednesday, the president declared that the California senator is "bad on facts" and predicted she will be a "big failure" in a match-up against his VP Mike Pence.
In her first remarks as a just-named vice presidential candidate, Senator Harris said the president's "failure" to take the coronavirus pandemic seriously, along with his "delusional belief he knows better than the experts", has led to millions of unemployed and infected Americans.
"Like everything else he inherited," the president ran a rising economy "straight into the ground," she said.
The president continued to defend his administration's response to the pandemic, dubbing the US the "ventilator king" and leading a panel at the White House to push for schools to reopen
"We've done a great job," he said during a briefing.
In Georgia, where in-person classes recently resumed in some district, in-person learning at one high school has been suspended as of 12 August, with a tentative reopening date for 31 August, after the school found 14 positive Covid-19 cases. Nearly 300 students and staff are now under quarantine, the school announced.
The president has meanwhile endorsed a far-right QAnon-supporting congressional candidate in Georgia following her win in the state's Republican primary on Tuesday. Progressive congresswoman Ilhan Omar, whom the president and his allies have frequently targeted, also handily defeated her well-funded Democratic primary challenger.
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