For an increasingly diverse and liberal Democratic Party, it seemed strikingly off-key when Joe Biden on Tuesday night warmly recalled his working relationship in the 1970s with two virulent segregationists, Sens. James O. Eastland of Mississippi and Herman E. Talmadge of Georgia.

On Wednesday, Biden faced his sharpest criticism yet from his 2020 presidential rivals, including from the two black Democrats in the field. Sen. Kamala Harris of California said the former vice president “doesn’t understand the history of our country and the dark history of our country,” and Sen. Cory Booker said Biden should immediately apologize for using segregationists to make a point about civility in the Senate.

Even some of Biden’s senior campaign advisers were privately shaken by the remarks. Yet Biden’s campaign appeared unbowed and intent on defending, or at least explaining, his worldview of politics, which is rooted in the 1970s when he came to the Senate and worked with those two Southerners and others he often disagreed with.

“Apologize for what?” he said Wednesday evening, saying that he “could not have disagreed with Jim Eastland more.” “Cory should apologize. He knows better. There’s not a racist bone in my body. I’ve been involved in civil rights my whole career, period, period, period.”

For many Democrats, Biden’s fond remembrance of working with two defenders of segregation, and his decision to highlight those relationships, seemed deeply misguided and out of touch with political change in America.

“I just really don’t understand for the life of me what the vice president could have been thinking, to bring the names of Talmadge and the others who are well-known conservative segregationists into any conversation referencing civility,” said Leah Daughtry, a veteran Democratic strategist who ran the 2008 and 2016 Democratic National Conventions and is African-American. She added, “He needs to issue an apology immediately.”

Biden, who is running for president in part on a message of national unity and reaching out to those with different viewpoints, particularly courted Eastland, despite his racist views and remarks.

The two men developed an “unlikely relationship,” as Biden put it in his 2007 book, as Eastland helped Biden achieve his first seat of power on the Senate Judiciary Committee. Biden and Eastland sharply disagreed on several civil rights-related matters, but they were also convenient allies, as both were vocal opponents of school integration through busing, a controversial topic at the time.

According to archives of The News Journal, the main newspaper serving Biden’s hometown, Wilmington, Delaware, he would also go on to present himself as a go-between on the Judiciary Committee for conservatives like Eastland and liberals like Sen. Edward M. Kennedy of Massachusetts, and to say that his criminal justice positions are “‘equidistant’ between the two factions.”

For Biden, the early Democratic front-runner, his remarks about Eastland and Talmadge — and the pointed criticism he drew on Wednesday — are a sharp example of how much Biden’s long record can be as much baggage as résumé.

Far from running away from his past, he has, in his 7-week-old campaign, proactively brought up his ties to multiple politicians who had records of opposing the civil rights movement, from Eastland and Talmadge to arch-conservative Sen. Jesse Helms, R-N.C. Biden routinely characterizes that era and those relationships as more civil and functional, with less demonization of the other side, even amid vigorous clashes over explosive issues like race.

Biden faces an unusual political dynamic: He is seeking to run against President Donald Trump, who has his own heavy baggage and record of divisive positions and remarks. Yet Trump’s supporters have appeared willing to forgive or look past the president’s political troubles. Biden may be leading in the polls, but he faces a Democratic electorate that is far from sold on his candidacy and may not be willing to shrug off comments, past votes and ghosts from the past — especially when Biden himself keeps bringing them up.

“He’s already looking ahead to the general election,” said Adrianne Shropshire, executive director of BlackPAC, a political advocacy group. “White swing voters may be persuaded by his ability to work across the aisle with segregationists. But that’s not an argument that’s going to work for black Democratic primary voters.”

The remarks also raised questions about Biden’s political instincts as even allies privately said he could have made a similar argument about his amicable dealings with people who held opposing views without extolling his relationship with notorious segregationists.

One of the Biden campaign’s operating assumptions is that Democratic voters are more interested in bipartisanship than the loudest liberal voices on Twitter would suggest — but some allies implied Wednesday that Biden’s references overshadowed the broader point about civility he was trying to make.

Some pointed to moderate Republicans like former Sens. Bob Dole of Kansas or John McCain of Arizona — for whom Biden delivered an emotional eulogy last summer — as better names to mention, a discussion that came up internally.

In a separate sign of possible turbulence for Biden’s candidacy, his campaign experienced the first departure of a prominent political consultant. Mark Putnam, a high-profile Democratic strategist and producer of television ads, confirmed in a brief phone call that he had recently left Biden’s campaign.

Putnam declined to address the reasons for his departure, though they did not appear to be related to Biden’s struggles over the last few weeks concerning abortion rights and race. “I wish the vice president well,” Putnam said.

Publicly, Biden did not address the issue during the day. Several advisers to Biden made a concerted public effort to explain and justify his remarks, saying that he was not praising segregationists but rather making a point about working with people with whom one disagrees. Several prominent African-American lawmakers defended Biden’s remarks as well.

But a number of Biden’s advisers used language about Eastland and Talmadge that was far harsher than Biden’s remarks on Tuesday.

Anita Dunn, a veteran Democratic operative, appeared on MSNBC on Wednesday afternoon to cast the segregationist senators as men Biden had long disagreed with on fundamental issues. She noted in particular Biden’s clashes with Eastland over the Voting Rights Act. Despite those differences, she argued, “There was civility involved.”

But she did not walk back his references to the two senators, which, as she said, Biden has made for years.

“You have to be able to work with people, even if they hold positions repugnant to you, in order to make some progress,” said Dunn, a Biden adviser. She went on to note that other presidential candidates, including Booker and Sen. Elizabeth Warren of Massachusetts, had worked more recently with Republicans who “are espousing views that are anathema to many people in the Democratic Party.

Biden had a similarly mixed relationship with Sen. Strom Thurmond, R-S.C., who had a history of racist views and was a key figure on the Senate committee in the 1980s and 1990s.

Though Biden and Thurmond had several disagreements over civil rights, they worked closely on crime legislation in the 1980s and 1990s. In 1997, Biden effusively praised him, including glowing words for Thurmond’s life before public office.

“Long before he was a committee chairman; indeed long before he came to the Senate so many years ago, Strom Thurmond was the consummate public servant,” Biden said.

Biden punctuated his speech with a joke: “Though he holds the record for the Senate’s longest filibuster, Strom Thurmond is a doer rather than a talker.”

He left out what Thurmond was filibustering when he set the record: the Civil Rights Act of 1957, which established the Department of Justice’s Civil Rights Division.

Historians stressed on Wednesday that Biden’s relationships with the Southern senators were hardly unusual for the time.

“What Biden did in dealing with these guys was no different than what JFK, LBJ or anybody else who wanted to get anything done in the Senate had to do at that point,” said James C. Cobb, a professor of history emeritus at the University of Georgia, referring to former Presidents John F. Kennedy and Lyndon B. Johnson.

A number of prominent African-American lawmakers and community leaders also came to Biden’s defense on Wednesday.

“I don’t see anything different in what Biden said to what we all do over here,” said Rep. James E. Clyburn, D-S.C., the House majority whip and highest-ranking African-American in Congress. “He didn’t say anything more than I would say to describe my work with Strom Thurmond and a few others.”

Clyburn, who participated in civil rights demonstrations in the 1960s and 1970s, said that Democrats of his generation needed to develop working relationships with segregationist Southern politicians like Thurmond, his state’s longtime senator.

When a reporter asked Clyburn if it mattered that the men Biden praised “used the ‘N-word,’” he shot back: “So what? You know how many times I was called the ‘N-word’ and worse?”

The Rev. Joseph Darby, an influential African-American pastor from Charleston, South Carolina — a state where polls currently show Biden with a commanding lead among black voters — dismissed the notion that Biden should apologize.

“People look at his overall record rather than cherry-picking some of the things he says,” said Darby, a longtime ally of Biden’s who also spoke positively about Harris and Warren. “They weren’t the examples I would use, but I don’t think that merits an apology. He was talking about the way the Senate used to work. That’s the way the Senate used to work.”

This article originally appeared in The New York Times.