Sessions’s chief of staff, Matthew Whitaker, will assume the role of acting attorney general until a permanent replacement is named. Whitaker will oversee the Mueller investigation, which has so far led to the convictions and guilty pleas of Trump allies including campaign chairman Paul Manafort and former personal lawyer, Michael Cohen. Though the former Alabama senator was one of the president’s earliest and loudest supporters, he has been on the receiving end of Trump’s consistent and public grievances.

“Sessions should have never recused himself, and if he was going to recuse himself, he should have told me before he took the job and I would have picked somebody else,” the president told the New York Times in a July interview.

The president has also lambasted Sessions for his management of the Justice Department, though Sessions has largely worked to make good on Trump’s campaign promises by shifting legal focus away from protection of civil rights in favor of measures of “law and order” in the name of immigration reform and national security.

Reaction from Democratic leadership has been swift. Ranking House Judiciary member Jerry Nadler took to Twitter demanding answers about the timing of the announcement, and Minority Leader Chuck Schumer told reporters that any resulting interference with the special investigation would be considered a “constitutional crisis.”

Whitaker, a former US attorney from Iowa who serves as director of the conservative ethics watchdog group Foundation for Accountability and Civic Trust, published an opinion piece for CNN in 2017, before he had joined the Justice Department, which was titled “Mueller’s Investigation into Trump has Gone too Far.”

Rebecca Linde is a writer and cultural critic in NYC. She tweets about pop culture and television @rklinde.