Democratic presidential candidate Joe Biden has picked Californian senator Kamala Harris as his running mate, he announced days before the Democratic convention on Monday.
Ms Harris is the first Black woman to be a vice presidential candidate.
She competed against Mr Biden in the Democratic primaries but ended her campaign before the Iowa caucuses in February.
Ms Harris is the daughter of immigrants, an Indian mother and a Jamaican father.
Mr Biden announced the decision in an email to supporters and on social media. He called her a “fearless fighter for the little guy and one of the country’s finest public servants".
Ms Harris accepted the nomination on Twitter and praised Mr Biden.
“Joe Biden can unify the American people because he's spent his life fighting for us," she said. "And as president, he'll build an America that lives up to our ideals.
“I'm honoured to join him as our party's nominee for vice president and do what it takes to make him our Commander-in-Chief.”
The decision followed months of vetting, online fundraisers and media appearances for more than 10 female candidates.
Ms Harris, 55, was born in Oakland, California, and was elected attorney general for the state in 2010.
In 2017, she became the second Black senator in US history and the first South Asian American in that position.
During her short run for the presidency, Ms Harris clashed with Mr Biden in the debates, attacked his record on busing and accused him of working with segregationists.
“There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day. And that little girl was me,” she said then.
The exchange soured the relationship between the two but with Ms Harris dropping out of the race, endorsing Mr Biden in March and then raising funds for him, they were able to bury the hatchet.
At an event in Delaware last month, he was seen carrying a notebook that read: “Do not hold grudges.” “Campaigned with me and Jill.” “Talented.” “Great help to campaign.” “Great respect for her.”
Those were in reference to Ms Harris.
The vice presidential selection process has been shrouded in secrecy and the Biden campaign has kept a lid on meetings and interviews he had with the candidates last week.
In March, he announced his intention to pick a woman for the post and the campaign has examined a list of governors, senators and congresswomen since May.
But it was Ms Harris, former national security adviser Susan Rice, Senator Elizabeth Warren and Michigan Governor Gretchen Whitmer who were chosen for meetings with Mr Biden on August 2, The New York Times reported.
After the killing of unarmed African American George Floyd by white Minneapolis police in May, and the Black Lives Matter protests, pressure grew on Mr Biden to pick a Black candidate to heal the racial divide.
Ms Harris brings generational balance to the ticket and she has pivoted to the left in the past few months, by sponsoring bills with progressive Senator Bernie Sanders, including one to provide monthly $2,000 payments during the pandemic.
She is known as an outspoken and fierce critic of the Trump administration in the Senate.
Last May, she called on Attorney General Bill Barr to resign after a testy exchange with him on the Senate floor over the Mueller report.
On foreign policy, Ms Harris is more of an unknown and is unlikely to overshadow Mr Biden.
She told the Council on Foreign Relations last year that the US should rejoin the Iran nuclear deal “as long as Iran also returned to verifiable compliance".
Ms Harris supports ending the war in Afghanistan with a political settlement.
On Israel and Palestine, Ms Harris voiced support for the two-state-solution and called Israel “a critical ally and friend, and its security is a top priority".
She and Mr Biden are due to appear at a fundraiser tomorrow and they will accept their nominations formally next week at the Democratic convention.