WASHINGTON — Joe Biden is under pressure to pick a Black woman as his vice presidential running mate. But polls suggest the most popular prospect among Black Democrats is white.

Sen. Kamala Harris, D-Calif., and Sen. Elizabeth Warren, D-Mass., are widely seen by Democratic officials and activists close to the process as front-runners, though other candidates remain in the mix and a Biden aide told NBC News that “the process is dynamic and ongoing and no final decision has been made.”

The two senators and former Biden presidential rivals have reached an advanced vetting stage that suggests they are formidable contenders, according to multiple people familiar with the process. Both women held fundraisers with Biden this month, with Warren’s event raising $6 million and Harris’s event $3.5 million.

In a CBS News poll last month, Warren topped the list of prospects that Democrats wanted Biden to consider, followed by Harris. Warren even led among Black Democrats — 72 percent said she should be considered, with 60 percent saying the same of Harris.

The competing imperatives present a challenge for Biden, pitting the prospect of making history with the first Black woman as vice president and the prevailing evidence that Black voters may prefer Warren. The topic has gained heightened scrutiny due both to Biden’s age and the elevation of race relations as an issue amid the backlash to George Floyd’s death.

“I don’t support an all-white ticket,” said Aimee Allison, the president of She the People, a progressive group that works to promote women of color in politics. “That was a tremendous mistake in 2016. We have a party that’s half people of color and a quarter Black. The ticket needs to reflect that.”

Allison said Harris would be one of several “excellent candidates” for vice president, citing the former California attorney general’s outspoken push for racial justice in recent weeks as the Senate debates police reform.

‘A Black face in a high place’ not enough?

Jorden Giger, a 29-year-old teacher and Black Lives Matter activist in South Bend, Indiana, disagreed. While he understands the need for a diverse ticket, he wants Biden to pick Warren.

“Descriptive representation is not enough. It’s not enough just to have a Black face in a high place,” Giger said by phone. “We need someone to actually champion our positions in a real way and she’s the best there is.”

Giger argued that Warren’s policy record, such as crafting the Consumer Financial Protection Bureau and her aggressive oversight of Wall Street, shows she’s “ready on day one” and resembles what the Black community needs.

In a Morning Consult poll last month, 24 percent of Black voters said a Warren pick would make them more likely to vote for Biden, while 19 percent said the same of a Harris pick.

A Civiqs-Data For Progress poll this month found that Stacey Abrams, a former Georgia legislator and gubernatorial candidate, is the top preference of Black Democrats. (Abrams said two weeks ago she hadn’t heard from Biden’s team.) Next was Warren, six points ahead of Harris.

An Economist YouGov poll this month found that Harris led Warren by two points among black Democrats asked for their vice presidential preference, inside the margin of error.

Other women of color who have received attention as potential picks include New Mexico Gov. Michelle Lujan Grisham; Rep. Val Demings, D-Fla.; Rep. Karen Bass, D-Calif.; Atlanta Mayor Keisha Lance Bottoms; and former national security adviser Susan Rice.

Bass, the chairwoman of the Congressional Black Caucus who played a leading role in the House-passed police overhaul bill this week, said she’s “not going to go there” when asked if she was being vetted by the Biden campaign.

The Biden campaign declined to say who is being vetted for the position. Aides to Warren and Harris would not comment for this article.

Biden, a former vice president himself, told donors in late May his team had been interviewing candidates and he hoped to announce his pick by Aug. 1, according to a pool report.

Generational contrast vs. economic credentials

“I have not made that judgment because we’ve just started now the deep dive in doing the background checks. They take six to eight weeks to get done. There are a number of African American women that are being considered, as well as Hispanic, as well as Caucasian,” Biden told WGAL News 8 during his Thursday visit to Lancaster, Pennsylvania.

One prominent Biden ally predicted he’d pick a woman with whom he has a relationship and faced on the 2020 debate stage, which would narrow it to Harris, Warren and Sen. Amy Klobuchar, D-Minn. Klobuchar bowed out of consideration last week amid scrutiny of her record as a former Hennepin County prosecutor who oversaw controversial police practices.

Klobuchar also took what many interpreted as a parting shot at Warren, calling on Biden to “put a woman of color on that ticket.”

Harris, who has Jamaican and Indian heritage, would make history as the first woman, first Black American and first Asian American to be vice president. She has one other advantage over a top rival: She’s 55, while Warren is 71. Biden, who would be 78 and the oldest president ever to take office, has offered himself as a transitional candidate serving as a bridge to the next generation.

“My challenge here is to have two candidates who in their 70s — it sort of ages out. I don’t think we’ve ever had a ticket where two candidates had a combined age of about 150,” Peter Hart, a Democratic pollster who helps conduct the NBC/Wall Street Journal survey, said in an interview.

Warren’s allies are selling the former Harvard law professor as a strong governing partner to Biden as he seeks to rebuild an economy in tatters. They point to her strengths with young and left-wing voters, a weakness for Biden, as evidence that she’s the best option to limit defections to the Green Party, which were devastating to Hillary Clinton in 2016.

Her detractors say Warren’s comparably left-leaning stances could make her a lightning rod for Republican attacks in the fall.

“The critical element that Joe Biden needs is somebody who is perceived as ready from day one to be president,” Hart said. “The whole campaign against him by Trump is going to be based on one idea: That he’s ‘Sleepy Joe, and boy I wonder if he’ll even be around when it comes to Inauguration Day.’ So you have to pass the competence test.”