Harris, the only black woman serving in the U.S. Senate, has marched in the streets and sponsored new police reform legislation on Capitol Hill. She has been a forceful proponent of sweeping social change and a fierce critic of President Donald Trump.
The 55-year-old senator from California also has become a key ally for Democratic presidential candidate Joe Biden, poised to challenge the Republican president in the Nov. 3 U.S. election, at a time when race has been thrust to the forefront of the campaign.
With Biden, 77, facing pressure within his party to choose a black woman as his running mate, Democratic donors, strategists and those close to his campaign said in interviews they think Harris is increasingly the likely pick.
The day after Biden flew to Houston and met with the family of George Floyd, the African-American man whose death last month in Minneapolis police custody spurred the civil unrest, Harris chaired an online fundraiser that netted Biden $3.5 million.
"She understands the moment," said Marc Lasry, Avenue Capital Group chairman and a member of Biden's national finance committee. "They want someone who will galvanize people. She seems to be that person."
A Democratic strategist with relationships in Biden's circle was even more blunt, saying recent events all but required Biden to pick a black woman – and that Harris is the most practical choice.
"It's going to be Harris. It was always going to be Harris. It was going to be Harris even when Joe Biden didn't think it was going to be Harris," said the strategist, speaking on condition of anonymity. "At some point, he was trying to convince himself black people like him so much that he could pick someone like Amy Klobuchar."
Klobuchar, a U.S. senator from Minnesota who is white, has seen her vice presidential prospects damaged as some black activists call her record as a former prosecutor on police misconduct in the county where Floyd died disqualifying.
Harris also is a tougher sell for Democrats in the party's left wing, who have criticized her record as a former prosecutor and attorney general in California including what they viewed as a failure to crack down on police misconduct.
Skeptics remained after Harris co-sponsored a Democratic bill this week that would ban chokeholds and remove some legal protection for police officers.
"She has a history that by some accounts is not good, but we want to see where she wants to move to," said Judith Browne Dianis, executive director of Advancement Project, a multi-racial liberal advocacy group.
'She's found her voice'
Laurie Levenson, a professor at Loyola Law School in Los Angeles who has been critical of Harris, said she has seen a new confidence and idealism in the senator since her presidential run ended last December.
"She's found her voice," Levenson said. "She's part of a movement."
Biden and Harris had some spiky exchanges last year during the Democratic presidential race. Harris slammed him at a debate for his record on mandated busing as a means to desegregate schools. Some Biden advisers have told Reuters the attacks made them question whether she would be loyal because of her political ambitions.
Tom Sacks-Wilner, who serves on Biden's finance committee, called that "water under the bridge" and said Democratic donors he knows are increasingly getting behind the idea of Harris joining the ticket.
Neither Biden nor Harris' offices would comment. Biden has said he hopes to announce his vice presidential choice by Aug. 1. Harris has said Biden should select whoever can help him beat Trump.
During Tuesday's fundraiser, Biden said the two former rivals now talk often. "She's been a fighter and a principled leader," Biden said.
Their main connection had been through Biden's son Beau, who served as Delaware's attorney general when Harris held the same post in California. Beau Biden, who died of brain cancer in 2015, and Harris worked on a number of issues together.
At the fundraiser, Biden spoke of a moment when he ran into Harris in Philadelphia after Beau's death and she gave the former vice president a hug and told him, "I love you, and I loved Beau."
"I won't forget that," Biden said.
Other black women under consideration by Biden include Atlanta Mayor Keisha Lance Bottoms and U.S. Representative Val Demings of Florida. Both lack Harris' deep background in public office and politics.
Theodore Johnson, an analyst on race and politics at New York University Law School's Brennan Center for Justice, said, "For those who still doubt her abilities or dislike her, I'm not sure there is much that can win them over. But for everyone else that Democrats will need to win the White House, I think her stock has increased."