Former Vice President Joe Biden punched back at Sen Cory Booker (D-NJ) on Wednesday for calling him the “architect of mass incarceration.”

Biden, who is attempting to shed his law and order image, claimed through his deputy campaign manager, Kate Bedingfield, that if anyone had “hard questions to answer” over their role in expanding the prison population it was Booker. The comments were made in response to Booker criticizing the former vice president for pushing criminal justice reform after having spent decades championing tough-on-crime measures.

“The absurdity of this attack is obvious,” Bedingfield said. “It is Senator Booker, in fact, who has some hard questions to answer about his role in the criminal justice system.”

She elaborated that as mayor of Newark, New Jersey, Booker pushed a zero tolerance policy for minor offenses, which “enmeshed many undeserving people in a criminal justice system that cast a huge shadow over their subsequent lives.” Bedingfield further asserted that Booker’s tenure coincided with widespread civil rights abuses by the Newark police department. The “nightmare,” according to the Biden aide, became so fraught that the Department of Justice was forced to intervene.

“Thousands and thousands of people — predominantly African American — were stopped by Booker’s force without legal basis,” Bedingfield said.

The former vice president, himself, echoed the argument on Wednesday during a campaign stop in Michigan.

“His police department was stopping and frisking people, mostly African American men,” Biden said, before claiming that Booker had “objected to federal interference” as mayor.

The criticism of Booker comes one day after he lambasted Biden for releasing a criminal justice reform proposal that “falls short of the transformative change our broken … system needs.” Booker was eager to note that Biden had spent nearly his entire career in Congress pushing many of the policies he was now seeking to reform.

“Joe Biden had more than 40 years to get this right,” the New Jersey Democrat stated. “The proud architect of a failed system is not the right person to fix it.”

Booker continued his attack on Wednesday, even calling Biden the “father of mass incarceration.”

“For a guy who helped to be an architect of mass incarceration,” the New Jersey Democrat told reporters after an NAACP presidential forum in Detroit, Michigan, “this in an inadequate solution to what is a raging crisis in our country.”

The fight between the two men comes ahead of the second Democrat presidential debate next week, where criminal justice reform is likely to be a significant topic. Biden, whom most polls show is still the frontrunner, albeit with a narrower lead than when he started the race, is particularly vulnerable on the issue.

As a senator, he helped author the 1994 crime bill, which many believe disproportionately singled out black males for longer prison sentences. The legislation is especially hated among the more progressive elements within the Democrat base. Biden has only raised the ire of some by remaining defiant about the legislation, at one point even claiming the notion it “generated mass incarceration” is wrong.

Heading into the debate, Biden’s team appears keenly aware of his weakness and is seeking to preemptively counter any attacks likely to emerge.

“Since next week’s debate format will give Senator Booker twice as much time to make his attacks than it allows Vice President Biden to respond to them, we thought we would begin to respond now,” Bedingfield said.