Senator Kamala Harris formally accepted the Democratic nomination for vice president on Wednesday night, in the party’s first virtual convention.
Ms Harris joins Joe Biden's campaign against Donald Trump as the first Black woman on a major party ticket.
She used her acceptance speech to share personal details about her immigrant parents and her upbringing. Ms Harris said she imagines an America built on the values her mother taught her, “where all are welcome, no matter what we look like, where we come from, or who we love.”
"My mother taught me that service to others gives life purpose and meaning," she added.
The nomination is the latest in a lifetime of firsts for the 55-year-old daughter of a Jamaican father and Indian mother.
Ms Harris 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.
She is now the first Black woman to feature on the ticket of a major US political party and is seeking to become the first female vice president of the US.
Ms Harris also made pointed remarks about race relations in US, while condemning Mr Trump for furthering inequalities.
"Donald Trump's failure of leadership has cost lives and livelihoods," she said. "We are a nation that is grieving."
She said structural racism is why "Black, Latino and Indigenous people are suffering and dying disproportionately," from the coronavirus. "There is no vaccine for racism."
"We have a president who turns our tragedies into political weapons, Joe will be a president who turns our challenges into purpose," she said.
The California senator spoke from Wilmington, Delaware, Mr Biden's home town, which has become the campaign headquarters. The Biden campaign has been largely run online due to the coronavirus pandemic, while Mr Trump has continued to hold rallies and host campaign events.
Kamala Harris slams Trump's 'failure of leadership'
Barack Obama, America's first black leader, used his Democratic convention speech on Wednesday night to depict President Trump as someone who never took his office seriously, putting US democracy in danger.
“What we do in these next 76 days will echo through generations to come," he said.
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."
"But he never did," Mr Obama said.
Instead Mr Trump has treated the presidency as "one more reality show that he can use to get the attention he craves."
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," he said.
Mr Obama took a back seat during the hotly contested Democratic primaries but is now throwing his still considerable sway behind Mr Biden, who served as Mr Obama's vice president for eight years.
Addressing all Americans, but naming White factory workers, Black moms, new immigrants and cynical young people, he said "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."
Mr Obama spoke two days after his wife, Michelle Obama, opened the convention with a scathing takedown of Mr Trump, painting him as a man who lacks the competence, character and decency for the job.
"Donald Trump is the wrong president for our country," she said.
Obama calls Trump's presidency 'one more reality show'
Former first lady Hillary Clinton, who lost the 2016 presidential election to Mr Trump, also addressed the convention to endorse Mr Biden.
Ms Clinton took aim at Trump's record as president, before urging Americans to vote. "We need numbers overwhelming, so Trump can't sneak or steal his way to victory," she said. "Vote for honest elections, so we, not a foreign adversary, choose our president."
"Let's set our sights higher than getting one man out of office," she added, telling Americans to vote for health care, for better jobs and for climate change. "Vote for justice, for George Floyd," she said.
Other speakers on the bill included Nancy Pelosi, Speaker of the House of Representatives, who blasted the Trump administration for its handling of the coronavirus pandemic. She is currently embroiled in negotiations with Republicans for a new stimulus bill to address Covid-19's crippling impact on the US economy,
"Instead of crushing the virus, they're trying to crush the affordable care act," she said.
Mr Biden was officially nominated on Tuesday to take on Mr Trump in the November 3 election. He will deliver an acceptance speech on Thursday at the conclusion of the four-day convention.
The Republican Party is to hold its online convention next week and nominate Mr Trump to try for four more years in office.
