Democratic presidential candidate Joe Biden on Tuesday tapped Senator Kamala Harris of California as his choice for vice president, his campaign told supporters in a text message.
Harris, 55, becomes the first Black woman on a major presidential ticket in U.S. history and providing him with a partner well suited to go on the attack against Republican President Donald Trump.
"I have the great honor to announce that I've picked Kamala Harris - a fearless fighter for the little guy, and one of the country's finest public servants - as my running mate," Biden said on Twitter.
With social unrest over racial injustice and police brutality against Black Americans rocking the country for months, Biden had been under increasing pressure to select a woman of color as his running mate. She is also the first Asian-American on a major presidential ticket.
In Harris, a senator from California who made her own run for the White House before ending it and endorsing Biden, he gains a deeply experienced politician already battle-tested by the rigors of the 2020 presidential campaign as they head into the final stretch of the Nov. 3 election.
Harris, who became only the Senate's second Black woman in its history when she was elected in 2016, will be relied on to help drive the African-American vote - the Democratic Party's most loyal constituency. Four years ago, the first dip in Black voter turnout in 20 years contributed to Democrat Hillary Clinton's upset loss to Trump.
Biden, whose foundering campaign was rescued by Black voters in South Carolina's primary in February, needs their strong support against Trump. It will be crucial in battleground states such as Michigan, Pennsylvania and Wisconsin that Trump won by the slimmest margins in 2016 but where opinion polls now show him trailing his Democratic rival.
The Black vote is also central to Biden's hopes of winning Southern states Georgia and Florida that Trump carried four years ago but that opinion polls indicate will be competitive this year.
Biden served as vice president for eight years under President Barack Obama, the first Black U.S. president.
Harris, 55, a former prosecutor and state attorney general in California, is well known for her sometimes aggressive questioning style in the Senate, most notably of Brett Kavanaugh during his 2018 Supreme Court confirmation hearing.
As a presidential candidate, she also took Biden to task in a nationally televised debate over his past stances on mandatory busing for students as a means to desegregate schools. Some Biden advisers have told Reuters the attacks made them question whether she would be a trusted working partner because of her political ambitions.
While that exchange failed to boost her White House hopes, the Biden campaign will now look for her to train her prosecutorial fire on Trump and Vice President Mike Pence. Harris is scheduled to debate Pence on Oct. 7 in Salt Lake City, Utah.
The choice of a running mate has added significance for Biden, who will turn 78 in November and be the oldest person to become president if he is elected.
Biden's age also has led to broad speculation he will serve only one term, making Harris a potential top contender for the nomination in 2024. Some of his allies were concerned that would make her a bad fit for the No.2 job and questioned her loyalty.
Biden publicly committed to choosing a woman as his No. 2 in a March debate after discussing the matter with his wife Jill and had considered other former presidential rivals such as Senators Amy Klobuchar and Elizabeth Warren.
After the protests that erupted over the May 25 killing of George Floyd, a Black man, by a white policeman in Minneapolis, Biden's search focused predominantly on candidates of color.
Harris will be confirmed as Biden's running mate at the Democratic convention that begins on Monday, where Biden will also be formally nominated to challenge Trump.