Former US President Barack Obama on Wednesday assailed his successor, Donald Trump, as deeply unfit for the office he occupies and argued that voting for his former No. 2, Joe Biden, was necessary to ensure the survival of American democracy.

“He’s shown no interest in putting in the work; no interest in finding common ground; no interest in using the awesome power of his office to help anyone but himself and his friends; no interest in treating the presidency as anything but one more reality show that he can use to get the attention he craves,” Obama said of Trump during the third night of the Democratic National Convention.

After avoiding direct criticism for most of Trump’s first term, the scathing broadsides from Obama constituted an unusually harsh appraisal of one President by another — although Trump has rarely hesitated to attack Obama, often levelling accusations of misconduct without evidence.

Obama blamed Trump for the 170,000 Americans who have died from the coronavirus, the millions of jobs lost to the ensuing recession and the diminishment of the country’s democratic principles.

His assertion that Trump, a Republican, is incapable of meeting the demands of the presidency echoed the remarks from his wife, Michelle Obama, on Monday, that Trump “simply cannot be who we need him to be”.

“Donald Trump hasn’t grown into the job because he can’t,” Obama said. “And the consequences of that failure are severe.”

On Twitter, Trump suggested that Obama’s decision to endorse Biden only after his rivals dropped out indicated doubts about Biden’s candidacy. But on Wednesday, Obama endorsed Biden and Kamala Harris, saying they “actually care about every American, and they care deeply about this democracy”.