The former vice president tweeted his acceptance, which he will codify in a Thursday night address to close the Democratic National Convention. "It is the honor of my life to accept the Democratic Party's nomination for President of the United States of America," he tweeted minutes after receiving enough votes to clinch the nomination.
The dramatic moment played out without any cheering crowd in a packed arena. Instead, Mr Biden and his wife, former Second Lady Jill Biden, celebrated remotely with family members as the entire convention has gone virtual due to coronavirus. It came after an evening in which the Democratic National Committee and Biden campaign programmed two hours that toggled between dismal descriptions of the state of the United States under Mr Trump and a sales pitch that the former vice president is uniquely qualified for the office and to take on challenges like the Covid-19 pandemic.
Ms Biden, a teacher, delivered a keynote speech from a Delaware school that described her husband, following the death of his grown son Beau Biden, going back to work soon afterwards. "That's just who he is," she said, saying her husband often gives out his personal cell phone number to people when he campaigned pre-Covid. And speaking of the pandemic, she contended her husband's "strong shoulders" will allow him to move the US beyond its ongoing health crisis.
"His faith is in you, in us," Ms Biden said. "We just need leadership worthy of our nation. ... Honest leadership to bring us back together ... That's Joe."
Democrats also trotted out some political star power on the second night of their 2020 shindig.
Former President Bill Clinton hit Mr Trump hard, saying when it came to the advice of health experts about the coronavirus outbreak, the president "ignored it". He said the 45th chief executive "shrugged and said, 'It is what it is. ... Covid hit us much harder than it had to."
"The Oval Office should be a command centre," but under Mr Trump it is a "storm centre" with "nothing but chaos", describing the president as one who "defines the job as spending hours a day watching TV and zapping people on social media".
Mr Clinton told voters that if they want a TV-obsessed leader, "he's your man", adding: "Denying, distracting, and demeaning works great if you're trying to entertain and inflame. But in a real crisis, it collapses."
Former Secretary of State John Kerry received a plush speaking spot just after 10.30pm, saying when Mr Trump travels abroad on diplomatic business, "it's a blooper reel." His party's 2004 nominee for president, Mr Kerry contended that Mr Trump inherited a strong economy from the Obama administration in which he served but "like everything else he inherited, he bankrupted it".
The first major Democratic rising star to speak was Stacey Abrams, a former minority leader in the Georgia House, who painted Mr Biden as a strong leader and Mr Trump as a self-focused chief executive.
Ms Abrams said: "Our choice is clear: a steady experienced public servant who can lead us out of this crisis just like he's done before or a man who only knows how to deny and distract. A leader who cares about our families or a president who only cares about himself."
'Trump has quit on you'
Senate Minority Leader Chuck Schumer told voters Mr Biden would not give up in the face of challenges, claiming Mr Trump has waved a white flag against the coronavirus outbreak.
"President Lincoln, honouring the great sacrifice at Gettysburg, didn't say: 'It is what it is.' President Roosevelt, seeing a third of the nation ill-housed, ill-clad, and ill-nourished, didn't say: 'It is what it is.' America: Donald Trump has quit on you," Mr Schumer said, standing outside with the Statue of Liberty behind him.
As Democrats prepared for the second evening of their 2020 nominating convention, Mr Trump was on an unofficial campaign trip to Arizona, a possible battleground state with its 11 Electoral College votes.
Each one could help decide the election, with the president telling an audience in Yuma he expects a "close" finish on 3 November -- or whenever all the ballots are counted and certified. He had some sharp words for his general election foe.
"By the way, if Sleepy Joe Biden ever got in, China would own the United States. They'd own it. They'd own every one of these people. They'd own this building," Mr Trump said, referring to Chinese leaders. "They'd own the United States because Biden would give them everything for two reasons: No. 1, he's not smart. And No. 2, he's weak. China would own our country."
The president started his day reacting to a fiery speech by former First Lady Michelle Obama that ended the Monday night portion of the DNC in which she said he is "faking" his way through the job, stirring up racial tensions and is unfit for the office.
"Somebody please explain to @MichelleObama that Donald J. Trump would not be here, in the beautiful White House, if it weren't for the job done by your husband, Barack Obama," the president tweeted. "Biden was merely an afterthought, a good reason for that very late & unenthusiastic endorsement...."
Meantime, on Air Force One as the Democrats spoke, a senior administration official said they had erred by allowing progressive hero Bernie Sanders to say on Monday night that his far-left view now are "mainstream".
"You talk about a radical idea becoming mainstream," the senior official said, granted anonymity to be candid. "That speaks volumes to the independent voter, they may not be a progressive supporter. Now it speaks to those that are energetic about him but it's very problematic for that independent, undecided voter who says I don't want a radical idea to be mainstream."
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