Joe Biden is conducting an unusually open and public search for a running mate, promising to pick a woman, disclosing that he is looking at about a dozen choices and even confirming specific names — all as contenders jockey for the job in plain sight.

But behind the scenes, two prospects with national experience who are significantly younger than Biden are emerging as the early leaders in the eyes of top Biden allies, according to interviews with a half-dozen people in frequent contact with the campaign: Sens. Amy Klobuchar and Kamala D. Harris.

Although Biden’s search is just getting underway in earnest and there are no strong internal front-runners, according to a person familiar with the campaign’s selection process, many Biden friends, donors and other associates have privately and publicly expressed a preference for the two senators. And they said much of the talk around the campaign focuses on them.

“I would like to see it be Klobuchar or Harris,” said Michael Kempner, a public relations executive and Democratic donor, in a sentiment shared by other Biden allies.

For all the confidentiality of the vetting process, several glimpses have emerged. Among those Biden is consulting, beyond his formal vetting committee, are his wife, Jill, and former president Barack Obama.

Biden has confirmed that Michigan Gov. Gretchen Whitmer and Rep. Val Demings (D-Fla.) are on his list, and he has hosted Whitmer and Klobuchar on his podcast. Another prospect, former Georgia gubernatorial candidate Stacey Abrams, is slated to appear with Biden in a joint interview on MSNBC on Thursday night; she formally endorsed him this week.

Klobuchar (D-Minn.) and Harris (D-Calif.) are seen as tested politicians who experienced the rigors of a national campaign alongside Biden during the Democratic primaries, understand the inner workings of Congress and are ideologically similar to the presumptive nominee.

Biden, 77, would be the oldest person elected to the presidency, increasing the scrutiny of his potential vice president. And the pandemic has put an additional premium on political experience and familiarity with the workings of government.

Klobuchar and Harris represent starkly different political paths that have stoked considerable Democratic debate during the Trump presidency. Harris, the daughter of Indian and Jamaican immigrants, could excite nonwhite voters in urban areas who did not turn out four years ago. Klobuchar, a moderate who campaigns as a homespun Midwesterner, has become a beacon for Democrats hoping to reclaim some white working-class voters and Republicans who cast ballots for President Trump.

Biden has offered few hints on his thinking, leaving even some longtime confidants in the dark about his views. Those who know him best say that personal rapport will be a crucial factor and that his decision will be informed heavily by his experience serving as vice president to Obama, whom he faced in a presidential primary contest before the two forged a strong friendship.

“Klobuchar or Harris would fit right in with where Joe Biden was with Barack Obama in ’08,” said Dick Harpootlian, a South Carolina state senator who has known Biden for three decades but has not discussed the pick with him. The eventual choice, he said, has “got to be somebody he’s got some chemistry with.”

Biden said Wednesday on “Good Luck America,” a political show on Snapchat, that he is looking for someone who complements him, and he suggested he is consulting with Obama. “As Barack and I talk about it, I’m looking for someone who has strengths that I don’t have as much,” Biden told host Peter Hamby. “I’m not afraid to go out and find someone who knows more than I know about a subject.”

He added, “I’m looking for someone who I can feel comfortable having as the last person in the room giving me advice.”

Still, Harris and Klobuchar have vulnerabilities. Biden’s team was bruised by Harris’s sharp attacks on him over forced school busing in a debate last year, according to three people familiar with the dynamic who spoke on the condition of anonymity to provide a candid account of conversations with top aides. As recently as March, Jill Biden noted the attacks during a public discussion of potential running mates.

At the same time, Klobuchar’s inability to win many African American supporters in the primaries has drawn notice from Biden’s team. And news reports about her poor treatment of staff members have circulated widely in the party, raising questions about her management style.

Compounding their challenges are the other boldface names believed to be in the mix. They include Sen. Elizabeth Warren (D-Mass.), who has a loyal liberal following and has been speaking on the phone with Biden more frequently over the past few weeks, according to two people familiar with their conversations.

Abrams, an African American woman from Georgia who is seen as a longer shot, has frequently expressed interest in the job in media interviews.

Sen. Catherine Cortez Masto (D-Nev.), who has received praise from former Senate majority leader Harry M. Reid (D-Nev.), is not to be overlooked, Democrats with an eye on the process said. Neither is New Mexico Gov. Michelle Lujan Grisham, who like Cortez Masto is Latina.

Biden recently announced four co-chairs of his selection committee, which he said is organizing background checks. “It’s a deep, deep background check. It takes somewhere between five weeks and eight weeks to get it done,” Biden said at a virtual fundraiser on Wednesday, before the list is “narrowed down.”

He added that the team he assembled is “in the process of thoroughly examining a group of women, all of whom are capable in my view of being president. And there’s about a dozen of them. We’re keeping the names quiet because if anyone isn’t chosen, I don’t want anybody to think it’s because there was something that was a, some liability that existed.”

But prominent Democrats are not waiting to make their preferences known. During a recent phone call, the Rev. Al Sharpton said he told Biden that he would prefer if he chose a black woman to be his running mate, a move he recalled telling Biden would “mean a lot” since it has not been done and would “drive out a lot of voters for you.”

Sharpton said Biden heard him out but did not make a commitment. The former vice president reminded him of his prior commitment to appoint a black woman to the Supreme Court, Sharpton recalled.

Among the names Sharpton mentioned was Harris, who has suggested she would take the job. “I am honored to even be considered, if that is the case,” she said last month during an appearance on ABC’s “The View.” “But I have to be very, very honest with you. I am full-time focused on what we need to do to address the coronavirus.”

Harris has introduced bills in recent weeks aimed at constituencies she would probably try to woo if she were on the ticket. One measure, introduced with Rep. Ayanna Pressley (D-Mass.), targets billions in grants to small “historically underrepresented businesses,” including those owned by minorities and veterans.

Harris also participated in a town hall hosted by the Biden campaign on the pandemic’s disproportionate effects on black and Latino communities.

In a demonstration of her political and fundraising chops, the senator from California has also been hosting virtual meetups for Senate candidates, introducing donors to Democratic hopefuls in Maine, South Carolina and Montana.

Klobuchar has been seeking to strengthen her ties to African American leaders, following criticism from some activists that her record as a prosecutor showed little sensitivity to the black community. She has unveiled legislation to expand early voting and vote-by-mail that was backed by the Rev. Jesse Jackson, and she has partnered with Abrams to promote the bill.

The senator from Minnesota has also pushed the Trump administration to release data about coronavirus infections and death organized by race. She recently appeared at a virtual town hall sponsored by the NAACP to discuss the virus and expanding access to voting.

To many top Democrats, Klobuchar’s appeal lies in large part in her ability to help win white voters in the upper Midwest — especially Wisconsin, Michigan and Pennsylvania, which were key to Trump’s 2016 victory. She ran for president as a consensus builder, emphasizing many of the same themes as Democrats who captured suburban House seats in 2018.

“I think Amy Klobuchar may have a little bit of an edge because she’s one of those northern Midwestern states and she lasted well throughout the primaries,” said Steve Westly, a California investor raising money for Biden.

Rep. Matthew Cartwright (D-Pa.), an early Biden backer who represents a swing district Trump carried in 2016, said Klobuchar showed a personal side during the campaign that could mesh well with Biden.

“I think identity politics only gets you so far,” said Cartwright, who praised other prospective candidates more briefly. “What people really want to know is are we going to have an effective team in the White House.”

Aimee Allison, the founder of She the People, a political organization that mobilizes women of color, is unenthusiastic about Klobuchar, who she said fared poorly in her organization’s polling of nonwhite women.

“When we think about those Midwest states, we actually need to be thinking about Milwaukee, Detroit, Philly,” she said. “Those are black and brown cities.”

The Biden campaign has not disclosed the details of its vetting process, but similar efforts in the past have involved a multistage process that begins with a review of public records.

During the 2004 vetting process conducted for Democratic nominee John F. Kerry, lawyers created confidential reports of roughly 10 pages each on a pool of about 20 contenders, according to a person familiar with the process, who spoke on the condition of anonymity because they were not authorized to talk publicly.

The list was subsequently narrowed, leading to an interview phase for a smaller group, who were poked and prodded for personal, financial and political skeletons, as well as a more detailed forensic evaluation of their paper trails, including tax returns.

For many Democrats, the current turbulent environment provides an incentive to go with an established brand and familiar track record.

“You don’t buy tissue; you buy Kleenex,” said John Morgan, a top Biden donor who praised several of the prospects. “Klobuchar is Kleenex.”