Chicago, 21 August 2024 (dpa/MIA) — Former US president Barack Obama gave Democratic presidential candidate Kamala Harris a rousing endorsement as he delivered the closing speech of the second day of the party's national convention on Tuesday evening.

"America is ready for a new chapter. America is ready for a better story. We are ready for a president Kamala Harris," Obama told a cheering crowd in his adopted home town of Chicago.

"Kamala Harris is ready for the job. This is a person who has spent her life fighting on behalf of people who need a voice and a champion," the former president said.

Obama hit out at his Republican successor Donald Trump, who is squaring off with Harris in the race for the White House.

"Here is a 78-year-old billionaire who has not stopped whining about his problems since he rode down his golden escalator nine years ago. It's been a constant stream of gripes and grievances that's actually been getting worse now that he's afraid of losing to Kamala," Obama said.

"We do not need four more years of bluster and bumbling and chaos. We've seen that movie and we all know that the sequel is usually worse."

Earlier on Tuesday, Democrats officially confirmed Harris as their presidential candidate for the November 5 election in a purely ceremonial vote.

The delegations from all the states and US territories once again cast their votes for Harris, accompanied by music, lighting effects, short speeches and much cheering in the event hall.

Harris had already been officially selected by more than 4,500 party delegates to be the Democrats' presidential nominee in an online roll call earlier this month.

Harris, who was in Milwaukee campaigning, joined the Chicago nomination ceremony remotely. Harris said she and running mate Tim Walz were honoured to be the party's nominees.

Harris is set to give the keynote speech at the convention on Thursday night, marking the grand finale of the four-day event intended to celebrate the Democratic candidates and to boost their momentum for the remainder of the campaign. 

Harris has wiped out Trump's lead in national polls since Biden abandoned his campaign and endorsed Harris to succeed him a month ago. Crucially, she has closed the gap or overtaken Trump in the key battleground states that will determine the outcome of the election.

By the time the four-day Democratic National Convention ends, there will be just over 70 days to go until the election. As the contest enters its last phases, the party hopes the bash will propel Harris into the autumn.