Cory Booker is about to make history. NBC News:

Booker's office said Monday that the Senate historian had been unable to find any previous instance of a sitting senator testifying against a fellow sitting senator nominated for a Cabinet position.

Noting that "I'm breaking a pretty long Senate tradition," the New Jersey Democrat said Monday on MSNBC's "All In": "We've seen Jeff Sessions — that's Senator Jeff Sessions — consistently voting against or speaking out against key ideals of the Voting Rights Act, taking measures to try to block criminal justice reform."

"He has a posture and a positioning that I think represent a real danger to our country," Booker said.

Congressmen John Lewis of Georgia and Cedric Richmond of Louisiana= (Chairman of the Congressional Black Caucus) are also planning to testify against Sessions.