Democratic presidential candidate Joe Biden has named Kamala Harris as his running mate. She would be the first black woman and South Asian American in the role if elected.
Once a rival for the top job, the California senator of Indian-Jamaican heritage had long been considered the front-runner for the number two slot.
The former California attorney general has been urging police reform amid nationwide anti-racism protests.
Mr Biden will face President Donald Trump in the election on 3 November.
After Tuesday’s announcement, Ms Harris tweeted that Mr Biden “can unify the American people because he’s spent his life fighting for us. And as president, he’ll build an America that lives up to our ideals.
“I’m honored to join him as our party’s nominee for Vice President, and do what it takes to make him our Commander-in-Chief.”
Mr Biden and Ms Harris will deliver remarks in Wilmington, Delaware, on Wednesday afternoon on “working together to restore the soul of the nation and fight for working families to move the country forward”, the Biden campaign said.
At a White House news conference on Tuesday, Mr Trump, a Republican, said he was pleased with Mr Biden’s choice, adding that Ms Harris did “very, very poorly” in her effort to become the Democratic nominee.
In last year’s race to be the Democratic nominee, Kamala Harris showed herself to be a forceful speaker, launching blistering attacks on Donald Trump.
Ms Harris will take part in a debate with Mr Trump’s running mate, Vice-President Mike Pence, on 7 October in Salt Lake City, Utah.
Who is Kamala Harris?
Ms Harris, 55, dropped out of the presidential race in December after failing to make headway in her bid to win the Democratic nomination.
She repeatedly clashed with Mr Biden during the primary election debates, most notably criticising his praise for the “civil” working relationship he had with former senators who favoured racial segregation.
Ms Harris was born in Oakland, California, to two immigrant parents: an Indian-born mother and Jamaican-born father.
She went on to attend Howard University.
After four years at Howard, Ms Harris went on to earn her law degree at the University of California, Hastings, and began her career in the Alameda County District Attorney’s Office.
She became the district attorney – the top prosecutor – for San Francisco in 2003, before being elected the first woman and the first African American to serve as California’s attorney general, the top lawyer and law enforcement official in America’s most populous state.
In her nearly two terms in office as attorney general, Ms Harris gained a reputation as one of the Democratic party’s rising stars, using this momentum to propel her to election as California’s junior US senator in 2017. She was only the second black woman ever elected to the US senate.
She launched her candidacy for president to a crowd of more than 20,000 in Oakland at the beginning of last year.
Role Of Vide-President:
The role of a vice-president running mate isn’t clearly defined.
One of the traditional roles is to go on the offensive in exposing the opposition’s weaknesses.
Constitutionally, the vice-president steps in to the top job should the president die or leave office during his or her term.
Mr Biden will turn 78 in November, meaning should he be elected he will be the oldest US president in history.
His age means Mr Biden’s vice-presidential choice may come under extra scrutiny.
Only two other women have been nominated as vice-presidential candidates for a major party – Sarah Palin by the Republican party in 2008 and Geraldine Ferraro by the Democrats in 1984. Neither were on the winning ticket.
A woman of colour has never been appointed to a presidential ticket by either of the two main American political parties. No woman has won the US presidency either.