Kenny Thompson, a former Biden aide who is helping raise money for his campaign, said Biden’s long track record with black communities has built up a resilient base.

"Speaking as a donor and former staffer and being black, I knew the vice president's resonance with black voters was real," Thompson said. "And I think a lot of that was from his work in the Senate, but also from having the back of Barack Obama for eight years. That goes a long way."

While some black donors have told Biden his position could be under threat, Buttigieg’s inability to break in with black voters so far has been a major warning sign about his campaign in the polls, and that has extended to the donor world.

Last week during a private breakfast at his New York headquarters, Buttigieg met with half a dozen black businessmen to discuss racial issues. The meeting was one in a series of quiet conversations that Buttigieg has held with black leaders over the last year, with his policies and relations in the black community under the microscope, especially in the months since a police officer shot and killed a black man in South Bend last June.

On NBC’s “Today” show Tuesday, Buttigieg said that voters of color who are “laser-focused on defeating this president” will be drawn to him after his Iowa victory. But in New York, he focused on pitching his “Douglass Plan” for improving race relations, as well as discussing his handling of the South Bend shooting.

Buttigieg’s plans are okay, two people at the meeting said — but his pitch lacked both a sense of urgency about dealing with race and a sense of empathy for the challenges that black people are facing.

“He has an almost unimaginable inability to connect with black people," said one person who was at the meeting. Buttigieg's campaign has hired several black fundraisers to help it raise money, including Marcus Switzer, a senior adviser for fundraising on the campaign.

Bernie Sanders has gained significant support from nonwhite voters this election compared to 2016, but neither Sanders nor Elizabeth Warren has been working to court support from black business leaders as they wage anti-corporate campaigns. Those largely moderate donors worry voters are not interested in the progressives’ platforms.

“Black donors are sophisticated and they want to see candidates engage on a full-scale level. Right now, if I’m being transparent, I don’t think any of the candidates running are up for the challenge,” said Quentin James, founder of The Collective PAC, which raises money for black candidates. “People are frustrated. I don’t know how else to communicate that.”