Former First Lady Michelle Obama has warned Americans to “vote for Joe Biden like our lives depend on it” during her speech at the Democratic National Convention.

In remarks that capped off Monday night’s event, Mrs Obama offered a sharp rebuke of the Trump presidency, telling viewers he “has had more than enough time to prove that he can do the job, but he is clearly in over his head”.

“He cannot meet this moment,” she told the convention, held online due to Covid-19.

She added that “if you think things cannot possibly get worse, trust me, they can”.

Mrs Obama emphasised the need for all Americans to vote, making reference to the voters who stayed home in 2016 and helped deliver Donald Trump victory that year, even as he lost the popular vote.

“We’ve all been suffering the consequences,” she said.

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Former First Lady Michelle Obama, seen here during a book tour last year, has castigated President Donald Trump at the Democratic National Convention (Kirsty O’Connor/PA)

In contrast, she described Mr Trump’s Democratic presidential rival for the November election, Mr Biden, as a “profoundly decent man” who “knows what it takes to rescue an economy, beat back a pandemic and lead our country”.

Former Democratic presidential candidate Bernie Sanders also unleashed a scathing attack on Mr Trump, suggesting that under him “authoritarianism has taken root in our country”.

The Vermont senator said Mr Trump had proved incapable of controlling the coronavirus outbreak, coping with its economic fall-out, addressing institutional racism in the US and tackling climate change.

“Nero fiddled while Rome burned,” Mr Sanders said. “Trump golfs.”

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President Donald Trump cannot ‘meet this moment’, according to Michelle Obama (Evan Vucci/AP)

Mr Sanders, who finished second in the Democratic primary behind Mr Biden, struck a more optimistic tone when he thanked supporters who voted for him in 2016 and 2020 for helping to move the country “in a bold, new direction”.

He called on his backers, as well as those who supported other 2020 Democratic primary contenders or Mr Trump four years ago, to unite behind Mr Biden.

“My friends, the price of failure is just too great to imagine,” he said.