Kamala Harris has made history by accepting the Democratic nomination for vice president, while joining Barack Obama and Hillary Clinton to condemn President Donald Trump's profound "failure" as a leader.
Ms Harris, the first black woman on a major party's White House ticket, accused Mr Trump of turning "our tragedies into political weapons".
"Donald Trump's failure of leadership has cost lives and livelihoods," the former California prosecutor charged in her acceptance speech. "We're at an inflection point."
Kamala Harris and Joe Biden at the Democratic National Convention. Source: DNC via Sipa USA
“The constant chaos leaves us adrift, the incompetence makes us feel afraid, the callousness makes us feel alone. It’s a lot. And here’s the thing: we can do better and deserve so much more.
"Right now, we have a president who turns our tragedies into political weapons. Joe will be a president who turns our challenges into purpose."
Her speech served as a reintroduction to the country after her unsuccessful White House bid.
Ms Harris outlined her background as a child of immigrants from India and Jamaica who as a district attorney, state attorney general and now vice-presidential candidate shattered gender and racial barriers.
She said she was able to make history because of the trailblazing efforts of women before her who fought for the right to vote.
"That I am here tonight is a testament to the dedication of generations before me," she said. "
They organised, marched, and fought — not just for their vote, but for a seat at the table."
Mr Biden, who faces Mr Trump on 3 November, is due to give his own acceptance speech on Thursday, closing a Democratic convention held wholly online and on television due to coronavirus safety precautions.
Shortly before Ms Harris spoke, America's first black president, Barack Obama, delivered his own condemnation of Mr Trump - and appeal for Mr Biden's election.
Mr Obama said that on handing over the White House to Mr Trump in 2017, he thought the Republican "might show some interest in taking the job seriously; that he might come to feel the weight of the office and discover some reverence for the democracy that had been placed in his care".
The convention, which was expected to draw 50,000 people to the city, is now taking place virtually due to coronavirus pandemic concerns. Source: DNCC
"But he never did," Mr Obama said.
As a result, Mr Trump has left America's "worst impulses unleashed, our proud reputation around the world badly diminished, and our democratic institutions threatened like never before," Mr Obama said.
Mr Trump responded to their speeches by telling reporters that Mr Obama had been "a terrible president" and firing off a series of capital-lettered tweets questioning their allegiances to Mr Biden.
Former US President Barack Obama speaking during the third night of the 2020 Democratic National Convention. Source: DNCC
"WHY DID HE REFUSE TO ENDORSE SLOW JOE UNTIL IT WAS ALL OVER, AND EVEN THEN WAS VERY LATE? WHY DID HE TRY TO GET HIM NOT TO RUN?" he wrote of Mr Biden.
"BUT DIDN’T SHE CALL HIM A RACIST??? DIDN’T SHE SAY HE WAS INCOMPETENT???" he wrote following Ms Harris's speech.
Leave nothing to chance
Former first lady and secretary of state Hillary Clinton, who narrowly lost the 2016 presidential election to Mr Trump, pleaded with voters to take nothing for granted in another tight contest.
"This can't be another woulda-coulda-shoulda election," she said.
Others on the night's program included Massachusetts Senator Elizabeth Warren, who unsuccessfully challenged Mr Biden for the nomination, and Nancy Pelosi, speaker of the House of Representatives.
Former Arizona congresswoman Gabrielle Giffords, who has become a gun control advocate after being shot and severely wounded in a 2011 assassination attempt, also spoke, along with Emma Gonzalez, a survivor of the Parkland school shooting.
Young activists addressed the dangers of climate change and Hispanic immigrants made highly emotional critiques of Mr Trump's policies that they said had torn apart their families.
Much focus was on Mr Obama, who remains a giant force in the Democratic establishment.
Although he took a back seat during the Democratic primaries, he is now campaigning hard for Mr Biden.
"Tonight, I am asking you to believe in Joe and Kamala's ability to lead this country out of dark times and build it back better," he said in his speech.
Donald Trump's 'storm centre'
Mr Obama spoke two days after his wife, Michelle Obama, opened the convention with a scathing takedown of Trump as "the wrong president for our country."
"He cannot meet this moment," she said.
Tuesday's lineup featured two other former presidents - 95-year-old Jimmy Carter and Bill Clinton, 74, who called the Trump White House "a storm centre".
Former Secretary of State Hillary Clinton also spoke during the convention. Source: Democratic National Convention
Mr Biden, 77, the former Delaware senator who served as Mr Obama's vice president for eight years, was officially nominated on Tuesday.
Ms Harris's nomination is the latest in a lifetime of firsts for the 55-year-old daughter of a Jamaican father and Indian mother who were immigrants to the United States.
She was the first black attorney general of California, the first woman to hold the post, and the first woman of South Asian heritage to be elected to the US Senate.
The Republican Party is to hold its virtual convention next week and nominate Mr Trump to serve four more years.
Mr Trump has chosen the White House South Lawn as the location for his acceptance speech - a controversial decision given that presidents are legally required to separate their campaigning from taxpayer-funded governing.
