Joe Biden’s rivals for the Democratic presidential nomination continued to hammer him Friday for his views on school busing, with some questioning his commitment to using the federal government to intervene when states discriminate against African Americans.

During a prominent exchange during Thursday night’s debate in Miami, Sen. Kamala D. Harris (Calif.) questioned the former vice president on whether he was wrong to oppose busing to integrate schools in his home state of Delaware in the 1970s.

Biden replied that his opposition was not to busing but rather to federal intervention, saying “what I opposed is busing ordered by the Department of Education.”

In separate television interviews Friday, Harris and Sen. Cory Booker (N.Y.) — the two African American candidates in the crowded Democratic field — took Biden to task for his response.

“I literally leaned back in my couch and couldn’t believe that one moment,” said Booker, who watched the second round of the debate on television after participating in the first round on Wednesday night.

“I think that anybody that knows our painful history knows that on voting rights, on civil rights, on the protections from hate crimes, African Americans and many other groups in this country have had to turn to the federal government to intervene because there were states that were violating those rights,” Booker said during an appearance on CNN.

He went on to praise former presidents, including John F. Kennedy and Lyndon B. Johnson, for “having the courage to bring the federal government in to stop states from sanctioning the kinds of bigotry and bias that was so hurting African American communities.”

Harris made a similar argument during an appearance on MSNBC, saying she differs with Biden on states’ rights.

“I was actually a bit surprised to hear how he described, in defense of his position, his perspective on the role of the federal government, and in particular, he mentioned the Department of Education,” Harris said. “We have so many examples in history where states have limited or restricted people’s civil rights . . . We have certain values that are national standards, and we’re not going to let states compromise that.”