Biden revealed back in March that he planned to choose a woman as his vice presidential candidate. Later, as racial issues in US flared up, there was speculation that he would choose a non-white woman. Harris, a daughter of Jamaican and Indian immigrants, identifies as Black.
But Professor Nakayama Toshihiro, an expert on American politics at Keio University, says she brings more than simply racial diversity to the ticket.
"I think it was a very sound choice on the part of Biden. She basically had almost what Biden wanted in a vice presidential candidate," he says. "You know, gender is a factor. That she's a major African American politician is a factor as well. And she is known as a great debater. Furthermore, she's 20 years younger than Biden."
The 77-year-old Biden, if elected, will be the oldest president in US history, and there is speculation that he won't seek re-election. So Nakayama says the vice presidential candidate this time is more significant than usual:
"Biden himself and even his supporters see Biden's candidacy and potential presidency as being transitional in nature. I think Harris could be a potential 2024 candidate for the Democratic Party."
Harris was a prosecutor and California attorney-general before becoming a senator known for confronting the Trump administration. She has called for a lenient approach to illegal immigrants. Biden described her as smart, tough, and experienced, saying she is "ready to do this job on day one."
Nakayama believes that Biden chose Harris because of her ability and message rather than traditional calculations of geographical influence.
"As she is from California, this choice was not intended to win a specific state. No matter who the VP candidate is, the Democratic Party is going to win California," he says. "So I think it was more about the overall effect that Harris will bring to the Biden campaign. I think it does send a message to the world that America is a diverse country. And that although it has been a constant struggle, it is somehow still trying to build a multicultural community."
Nakayama predicts that President Trump will attack Harris as a radical, but says the tactic is unlikely to succeed.
"The Trump team is going to try to portray her as being an extremist and a radical. And though she has veered to the left during the primaries, I think it's going to be a bit of an overreach to paint her as being a radical. Many centrists within the Democratic Party did support her during the primaries."
On Wednesday, Harris gave a demonstration of exactly what she brings to the Biden campaign. In her first speech since being named as the running mate, she laid into the Trump administration for its handling of the coronavirus outbreak and called for America to do more to fight racism.
Biden and Harris are expected to be formally confirmed as nominees at the Democratic National Convention that begins on Monday. They will then have less than 80 days to run a campaign that will be groundbreaking for a great many reasons.