DELAWARE, USA (AP) — Former President Barack Obama warned Wednesday night that American democracy may not survive if President Donald Trump is reelected, a damning assessment of his successor intended to jolt Democrats into rallying around Joe Biden and doing whatever it takes to vote.

“Donald Trump hasn’t grown into the job because he can’t,” Obama charged, speaking from the Museum of the American Revolution in Philadelphia, a backdrop chosen to reinforce what the former president sees as the dire stakes of the moment.

“I have sat in the Oval Office with both of the men who are running for president,” Obama continued, describing Biden as his brother. “I never expected that my successor would embrace my vision or continue my policies. I did hope, for the sake of our country, that Donald Trump might show some interest in taking the job seriously.”

Obama’s remarks were striking for their bluntness, especially from a figure who has spoken fondly of the tradition of presidents refraining from publicly criticising their successors. But he reflected the Democrats’ view that the nation is facing an existential crisis as it confronts health and economic turmoil and a reckoning on racial justice. The party’s 2016 nominee, Hillary Clinton, echoed those warnings earlier in the evening.

Biden’s running mate, Kamala Harris, was capping the third night of the convention in a symbolic hand-off from Obama, the nation’s first black president, to the first black woman on a major party ticket.

The night focused on the party’s commitment to progressive values on issues like gun violence and climate change, while highlighting speakers most likely to connect with women and all people of colour, voters whose energy this fall could ultimately decide the outcome.

Democrats targeted Trump’s policies and personality throughout, casting him as cruel in his treatment of immigrants, disinterested in the nation’s climate crisis and over his head in virtually all of the nation’s most pressing challenges.

Above all, there was an urgent focus on voting.

Harris, the 55-year-old California senator whose parents are Jamaican and Indian, made a surprise appearance early in the programme, calling on supporters to have a specific “voting plan” to overcome the obstacles to voting raised by the coronavirus pandemic and postal slowdowns.

“When we vote things change, when we vote things get better, when we vote we address the need for all people to be treated with dignity and respect,” Harris said. “So each of us needs a plan, a voting plan.”