The campaigns of Pete Buttigieg, Elizabeth Warren, and Bernie Sanders’ campaigns all said that about 40 percent of their full-time campaign employees are people of color. Buttigieg's campaign added that just over half of its staff are women, while Warren's said over 60 percent of its staff is female, non-binary, or gender non-conforming.

Pressed on whether he would name a person of color as his running mate, Biden responded in the NPR interview by highlighting what he called the most diverse staff of the field. His most senior Latina staffer, Vanessa Cárdenas, recently left the campaign, as POLITICO first reported.

The Biden campaign's refusal to provide evidence backing the former vice president’s claim could provide an opening for his rivals to attack his veracity, as candidates work to create contrasts and score points ahead of the Feb. 3 Iowa caucuses.

“If the Vice President claims are true, and I have no reason to discount him, I would think he’d be absolutely thrilled to share the record so he can be compared,” said Leah Daughtry, a veteran Democratic strategist and former Democratic National Committee official. “If he’s got a story to crow about then listen, crow on. And let’s have the data to back it up the way the other candidate’s campaigns are providing it.”

Nina Smith, traveling press secretary to Buttigieg, said it's "not enough" to have a diverse staff; people of color must be placed in top positions and throughout the campaign, she said.

“Our campaign, we’re 40 percent people of color and we’re spread across departments,” Smith said Tuesday at POLITICO’s Women Rule Summit.

Biden continues to hold the majority of support from minority voters, especially black voters, leading his Democratic opponents in some cases by double digits. In a Nov. 18 Quinnipiac poll, Biden received 44 percent support from black voters, compared to 10 percent for Sanders.

Bakari Sellers, a prominent South Carolina supporter of Kamala Harris before she dropped out, said that even if Biden did exaggerate his staff's diversity, his bond with black voters is too strong for it to make a difference in the race. None of his Democratic opponents has come close to matching Biden on that front, Sellers said, adding that all Democratic campaigns, including Biden's, should be "praised" for hiring diverse staffs.

Democratic campaigns in 2020 are far more diverse than previous cycles, but Alicia Garza, co-founder of Black Lives Matter, said that voters “do notice when a candidate is inconsistent about their record."