Kamala Harris 'needs to be a validator for Joe Biden now,' says former White House communications director

With just under three months until Election Day, Joe Biden's vice presidential pick, Kamala Harris, "needs to be a validator for" for the presumptive Democratic nominee, said former Obama White House communications director Jen Psaki in an interview with ABC News' "Powerhouse Politics" podcast Wednesday.

"Has Joe Biden always historically had the best, most progressive record on race issues? No, he hasn't," said Psaki. "Does she feel confident that he has grown and he has somebody who is listening and wants to do the right thing? I hope she feels that way. Otherwise, she shouldn't have accepted the role."

Psaki was asked about a heated debate moment between the former rivals, turned partners in July, when Harris criticized Biden's past opposition to federally mandated busing as a means to desegregate schools. Biden has made clear that he doesn't "hold grudges," but that moment from more than a year ago re-entered the political conversation when Biden announced Harris would be his running mate on Tuesday.

Psaki, who also once served as the spokeswoman for the U.S. State Department, said that Harris needs to "have a better answer for why she feels comfortable" joining Biden on the ticket after that moment, which she said "felt harsh" to the Biden campaign, but she also noted that it highlights one of Harris' strengths.

"If you separate yourself from the personal side of that, it also shows that she's a very effective attack dog because not only did she attack him, she did it in a way where she weaved her bio in," Psaki told ABC News Chief White House Correspondent Jonathan Karl and Political Director Rick Klein. "If you're in the fight of your life, the race of your life -- you're trying to, you know, win the presidency, you want the people who are effective at that -- who can do that to Donald Trump."

Yvette Simpson, CEO of progressive political action committee Democracy for America (DFA), told the podcast in a separate interview that that moment in the debate is an example of Biden's difficulty being challenged by his own political history, but that Harris could help in that.

"We believe that Kamala Harris would be more likely to be responsive to the progressive viewpoint and may be willing to push or pull him along. And that is the expectation and the hope," Simpson, who is also an ABC News contributor, said.

While Harris wasn't progressives' "first or second choice," Simpson said she believes that Harris "may be able to buck the system," noting that the first-term California senator was endorsed by DFA during her 2016 campaign.

Harris has faced criticism for her prosecutorial record, but Simpson said she would "give her a little bit of grace" on that issue.

"Back then, the way that we know criminal justice reformers, they didn't really exist. If you were in the position of prosecutor, you aren't even empowered to take on the police union to make real changes at that time. ... I personally give her a little bit of grace as a lawyer, myself, not a prosecutor, to understand how challenging it was -- could have been for her," Simpson said. "She had said on many occasions, she got into the prosecutor's office because she wanted to change the system from the inside. Anybody who's ever tried to change the system from the inside knows how hard that is."

While Harris did run for president, Psaki said that she now has a new opportunity to reintroduce herself to the public, especially with her primetime speech at the Democratic National Convention.

"She is somebody who has been a rising star in the Democratic Party for more than a decade. She's somebody who has kind of been mapping her way through the system in California," Psaki said. "And even though she wasn't a successful presidential candidate, she also kind of dropped out at a strategically wise moment. Right. Because there was nobody who voted against her."

And of the other women who were on Biden's vice presidential shortlist, Psaki said, "we're gonna see them again," potentially even serving in a Biden administration cabinet position.