Justice Democrats, the group that was formed by Sen. Bernie Sanders’ (I-VT) 2016 campaign staffers, slammed former Vice President Joe Biden’s busing remarks during the second Democrat debate.

During the debate, Sen. Kamala Harris (D-CA) attacked Biden for opposing the practice of busing, wherin black children were bused to schools with mostly white children in order to desegregate them. Biden then claimed he opposed federally-mandated busing only.

Biden’s deputy campaign manager and communications director Kate Bedingfield told MSNBC later “At the time, many in the African American community, in the civil rights community, were saying busing was not the best way to integrate schools…and frankly, that’s been borne out today.”

Justice Democrats’ Executive Director Alexandra Rojas and Communications Director Waleed Shahid responded to her comments in a press release on Monday:

As Senator, Joe Biden was routinely criticized by civil rights leaders over his position on busing and desegregation. When Joe Biden could have apologized for being on the wrong side of history, he doubled down and appeared angered by Senator Harris’ remarks at the debate. Her argument, and his campaign’s refusal to own up to his past, made clear that Joe Biden lacks the leadership needed to govern America through a series of historic crises today.

According to polling released Monday by CNN/SSRS, Biden’s numbers slipped, while Harris’s surged nine points.

The incident and Biden’s inability to defend against an attack by Harris have raised questions over whether Biden can take on President Donald Trump in 2020.

The Justice Democrats — who helped elect a number of Democrats in 2016 — also listed news articles and op-eds from the past in the press release showing that an anti-busing amendment by Biden was opposed by a number of African American civil rights activists.

“The Biden amendment is thus a real threat not only to the gains of the sixties, but to decency in this society. Congress will be advancing the cause of justice by eliminating it from the bill,” a New York Times Editorial Board piece published on September 19, 29175 read.

Several clips showed that the National Association for the Advancement of Colored People (NAACP) opposed Biden’s anti-busing position.

“Specialists generally agree that the Eagleton‐Biden amendment will have a crippling effect on the H.E.W. Department’s ability to force desegregation of Northern school systems,” a New York Times article from February 8, 1978, read.