In a move that may be a first of its kind, Sen. Cory Booker, D-N.J., will testify against fellow Sen. Jeff Sessions when the Alabama Republican appears before the Senate Judiciary Committee.

Booker said he does not “take the decision lightly” to testify on Wednesday. Yet President-elect Donald Trump’s attorney general nominee has too many problematic policy stances and a record that is in his view “deeply troubling.”