As was hinted at in the lead-up to the debate on Wednesday, Booker and Biden hit each other for their records on criminal justice.

Booker began, calling out Biden for being associated with many crime bills during his time in the Senate and said he can’t just now come up with a plan for reform. Biden snapped back, saying those bills were passed overwhelmingly and he has since moved toward a path of reforming the criminal justice system.

Then Biden went after Booker’s record on criminal justice as mayor of Newark. Booker took over a city that was plagued with violent crime, and he pledged during his campaign to do whatever it took to curb the violence. His tough-on-crime agenda curbed violence early on, but his police department faced soaring complaints as residents alleged officers used excessive force, made unlawful stops, and engaged in racial profiling.

The American Civil Liberties Union called for reform, with the ACLU of New Jersey gave Booker a "D" when it came to "police practices" in 2009. But after slow progress, it petitioned the Justice Department the following year to take action, citing more than 400 allegations — most of which came during Booker's administration — the organization claimed were proof of police misconduct. The Justice Department would end up investigating the police department, and Booker eventually came around on the probe.

In the years since, Booker has been a champion of criminal justice reform. The senator was instrumental in passing the bipartisan First Step Act, signed into law last year. The senator has made many additional proposals aimed at reforming the criminal justice system.

Booker said Wednesday it was “no secret that I inherited” a police department with massive problems and decades long challenges. Booker said he was “shocked” Biden wanted to take on his criminal justice record, saying he was “dipping in the Kool-Aid” and “didn’t even know the flavor.”

“I embraced reform,” Booker said, “You’re trying to shift the debate for what you created.”

Biden has come under fire for his main piece of criminal justice legislation, the controversial 1994 crime bill that experts say contributed to mass incarceration. Of note, Booker, as mayor, utilized grants made available through the crime bill to help rehire Newark Police Department officers who were the victims of municipal budget cuts.