Shortly after Senator Bernie Sanders suffered a crushing loss in South Carolina’s Democratic primary in 2016, his campaign’s African-American outreach team sent a memo to top campaign leaders with an urgent warning.
“The margin by which we lost the African-American vote has got to be — at the very least — cut in half or there simply is no path to victory,” the team wrote in the memo, which was reviewed by The New York Times. Mr. Sanders had won 14 percent of the black vote there compared with 86 percent for Hillary Clinton, according to exit polls.
Over seven pages, the team outlined a strategy for winning black voters that included using social media influencers and having Mr. Sanders give a major speech on discrimination in a city like St. Louis or Cincinnati.
Mr. Sanders’s inner circle did not respond.
In a campaign in which Mr. Sanders badly needed his message against inequality to catch fire with black voters, the senator from Vermont and his senior leaders struggled to prioritize and execute a winning plan to build their support. Top aides lost faith in their African-American outreach organizers, whose leadership was replaced and whose team members were scattered across the country. Initiatives like a tour of historically black colleges and universities fizzled; Mr. Sanders even missed its kickoff event.
As Mr. Sanders prepares to announce another run for the White House as early as this week, his weak track record with black voters — a vital base in the Democratic Party — could be a potential threat to his candidacy. And his campaign’s experience in 2016, as described in interviews with nearly two dozen current and former advisers and staff members, reveals a strikingly uneven commitment on the part of Mr. Sanders and his top advisers to organize and communicate effectively with black voters and leaders.
For 2016, Mr. Sanders initially put together an all-white leadership team and campaigned heavily in predominantly white states like Iowa and New Hampshire, which vote early in the nomination process. The relationship between his inner circle and his black staff members frayed, and it is unclear if top Sanders aides were aware of the damage until it was too late.
As the primary season unfolded, Mrs. Clinton dealt Mr. Sanders a series of stinging defeats in Southern states with high black turnout, while African-American leaders repeatedly criticized the Sanders campaign for failing to understand the concerns and priorities of their constituents.
This year, Mr. Sanders is already dealing with another thorny problem involving his 2016 staff: allegations from women who say they were mistreated or harassed during the campaign. Last month, after The Times published an investigation into complaints by female staff members, Mr. Sanders publicly apologized.
The two issues could make Mr. Sanders vulnerable in a crowded and diverse Democratic primary field that includes several female and minority candidates.
Advisers to the senator maintain that the African-American outreach team had plenty of resources, and was a victim of its own inefficiency.
“The black people had the largest team — the Latino outreach team didn’t even have that many people,” said Symone Sanders, who took over black outreach efforts after the South Carolina primary. “And then what did they do with the resources? They squandered it.”
Dissatisfaction among black staff members on the 2016 campaign was reported at the time, including by Fusion. But fresh interviews show that many former black employees still feel frustrated that they were not taken seriously or provided the resources they needed to succeed — even though some continue to admire Mr. Sanders.
“It’s almost like they didn’t need us for anything,” said John Solomon, who was hired as an organizer but soon became disillusioned when campaign aides assigned him to drive people around Iowa in a truck. “It was kind of like, you have black staff just to say you have black staff.”
This tension spilled over into other areas of the campaign, particularly among local staff members in South Carolina, who worked closely with the African-American outreach team. Some black campaign workers described microaggressions — subtle interactions that, while not overtly discriminatory, still played on racial prejudice. One woman said her boss almost never spoke to her.
Mr. Sanders appears committed to strengthening ties with the black community since his loss to Mrs. Clinton. He has made multiple trips to the South, and last month he spent Martin Luther King’s Birthday in South Carolina, where he spoke at the Capitol and met with black leaders, elected officials and students.
At the same time, the senator’s advisers are conscious that any future presidential campaign would need a much more diverse staff, especially in its upper ranks. Last month, Jeff Weaver, Mr. Sanders’s former campaign manager and currently a senior adviser, acknowledged to The Times that the 2016 staff had been “too male” and “too white.”
Mr. Weaver declined to comment for this article. Friends of Bernie Sanders, the senator’s campaign committee, said in a statement that Mr. Sanders “remains committed to diversity and inclusion in the workplace, politics and in policy.”
The group also said it was having conversations and conducting training with human resources consultants and current and former staffers “with the goal of safe, inclusive and equitable policies that reflect the work and values of Senator Sanders.”
In any political campaign, the internal competition for resources can be fierce, and getting the ear of the candidate’s top aides is difficult.
In 2016, this frustration was particularly acute for those working on Mr. Sanders’s African-American outreach efforts. Many had joined with the goal of bringing the candidate’s populist message into black communities.
Danny Glover, a liaison to historically black colleges, introduced a tour he believed could solidify support from young black voters.
But Mr. Sanders did not attend the kickoff event at South Carolina State University, and the campaign often sent surrogates rather than the senator himself. The budget for the tour was soon cut, Mr. Glover said, and the events that were held were scaled back.
“It was kind of disappointing,” Mr. Glover said, adding, “I just think back to the opportunities we left on the field for lack of investment into it.”
The senator’s campaign committee said that Mr. Sanders “deeply cares about H.B.C.U.s” and that the United Negro College Fund planned to honor him next month.
Other staff members shared similar accounts of disappointment.
When Mr. Solomon joined the campaign in late 2015, he was told his job would include networking with black voters and planning events in black communities. But almost immediately he was assigned tasks like keeping itineraries and chauffeuring surrogates that had little to do with outreach — which made him feel like “support staff,” he said.
Roy Tatem, the deputy director of the outreach team, said higher-ranking aides, including Mr. Weaver, rarely interacted with the group as a whole, and that there was a constant push and pull for resources.
Mr. Sanders’s “heart has been consistently in the right place,” Mr. Tatem said. But he added that over time campaign leaders deprioritized black voters, especially after the South Carolina primary defeat. “The narrative became ‘Bernie cannot win black voters,’” he said.
After South Carolina, Symone Sanders, who is black (and is not related to the senator), was put in charge of winning over black voters. She said she knew that the outreach team was frustrated but added that “a large part of it is a lack of understanding for what the process and protocols should have been.”
She said the loss in South Carolina was partly because the campaign got there too late to overcome Mrs. Clinton’s built-in advantage, reflecting an overall disorganization. But she also said the outreach team did not adequately support on-the-ground workers there.
“They did not deliver,” she said in an interview.
Top aides said the campaign invested heavily in the outreach team, including giving it its own office in Atlanta.
“The individual roles of African-American outreach staff members changed as the campaign grew and the calendar progressed, as they did in every department,” the senator’s campaign committee said.
Advisers to Mr. Sanders say he is committed to having a more diverse campaign staff should he run again, and there have been signs he is trying to build his relationship with the black community. During his trip to South Carolina last month, he spoke to students at Benedict College, a historically black college, and met with clergy and members of the state’s legislative black caucus.
Representative James Clyburn of South Carolina, the No. 3 Democrat in the House, was with Mr. Sanders on Martin Luther King’s Birthday and said the senator’s speech there had a different tone than in the past.
“In South Carolina before, his speeches did not lend themselves to being embraced by the African-American community,” Mr. Clyburn said. Mr. Sanders’s recent speech, in which he called President Trump a racist, “showed much more sensitivity to the dreams and aspirations of African-Americans than his speeches did in 2016,” Mr. Clyburn said.
Separately, Mr. Sanders has been reaching out to black leaders — including Chokwe Antar Lumumba, the mayor of Jackson, Miss., and Derrick Johnson, the president of the N.A.A.C.P. — to discuss issues that affect black communities, like economic justice and voter suppression.
But he has had some missteps, too. Some critics cited recent remarks he made suggesting that white voters who were uncomfortable voting for black candidates were “not necessarily racist.” Others said his decision to deliver his own rebuttal to the State of the Union address was disrespectful to Stacey Abrams, a rising Democratic star and the first black woman chosen to give the official response.
Many former staff members said that above all, if Mr. Sanders runs in 2020, they wanted to see the makeup of his campaign staff — and whether people of color are empowered — before they were willing to assess his progress.
“He can start with the hiring process,” Mr. Glover, the college tour organizer, said. “Those first hires are going to let a lot of us know if he learned from the 2016 cycle.”