Rep. Alexandria Ocasio-Cortez (D-NY) joined the chorus of Democrat lawmakers criticizing former Vice President Joe Biden for touting his past working relationship with segregationists.

In an interview with Politico, Ocasio-Cortez accused the 2020 frontrunner of overlooking racial issues during his time in the U.S. Senate.

“If you ignore racism and if you don’t address issues of race with racists, then everything is fine, right?” Ocasio-Cortez said Wednesday. “That’s how you work with segregationists: By not confronting the racism and their institutionalization of second-class citizenship and a lack of fully recognizing African Americans.”

At a New York fundraiser Tuesday, Biden pointed to two segregationist senators, James Eastland (D-MS) and Herman Talmadge (D-GA), to argue that Washington functioned more smoothly a generation ago than under today’s “broken” hyperpartisanship.

“We didn’t agree on much of anything,” Biden said of the two men, adding that Talmadge as “one of the meanest guys [he] ever knew” and that Eastland called him “son,” though not “boy,” a reference to the racist way many whites addressed black men at the time.

Yet even in that Senate, Biden said, “At least there was some civility. We got things done.”

The former vice president’s rivals for the 2020 nomination, including the two major black candidates in the race, Sens. Cory Booker (D-NJ) and Kamala Harris (D-CA), roundly criticized Biden’s comments. However, Biden did not back down Wednesday and was particularly defiant in the face of criticism from Booker, who said the former vice president should apologize.

In response, Biden said Booker should apologize because the senator “should know better” than to question Biden’s commitment to civil rights.

“There’s not a racist bone in my body,” Biden said. “I’ve been involved in civil rights my whole career.”

Appearing on CNN, Booker shot back: “I was raised to speak truth to power and that I shall never apologize for doing that. And Vice President Biden shouldn’t need this lesson.”

“We’re all going to say things that are wrong, but to recognize that and to take the step that you need for healing and reconciliation, to admit to that,” the New Jersey Democrat added. “So, for his posture to be, to me, ‘I’ve done nothing wrong. You should apologize. I’m not a racist’ is so insulting and so missing the larger point, that he should not have to have explained to him.”

It is becoming one of the most intense disputes of the primary, showing the hazards for Biden as he tries to turn his decades of Washington experience into an advantage. Instead, he is infuriating Democrats who say he is out of step with the diverse party of the 21st century and potentially undermining his argument that he is the most electable candidate to take on President Donald Trump.

The Associated Press contributed to this report.