Democrats poised to take charge of House committees come January are signaling that they want to investigate the replacing of former Attorney General Jeff Sessions with Acting Attorney General Matt Whitaker.

Top Democrats on multiple committees wrote to key Trump administration officials Wednesday night informing them that committees will be investigating Sessions' departure. They also said they will continue to conduct parallel investigations alongside special counsel Robert Mueller's probe, and urging them to preserve all relevant documents. Democrats are particularly interested in how Whitaker will oversee the Mueller probe, given his past comments questioning the scope of the investigation.

Deputy Attorney General Rod Rosenstein had been overseeing the investigation, but Sessions' sudden ouster Wednesday means that baton passes to Whitaker.

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When Democrats assume control of House committees next year, they will direct everything from the subject matter of investigations to the timing and substance of committee hearings. The will also have the power to issue subpoenas.

"Committees of the United States Congress are conducting investigations parallel to those of the special counsel's office, and preservation of records is critical to ensure that we are able to do our work without interference or delay," the Democrats wrote. The letter is signed by House Judiciary Committee Ranking Member Jerrold Nadler, House Intelligence Committee Ranking member Adam Schiff, House Oversight and Government Reform Ranking Member Elijah Cummings, and Senate Judiciary Committee Ranking Member Dianne Feinstein.

"Committees will also be investigating Attorney General Sessions' departure. We therefore ask that you immediately provide us with all orders, notices, and guidance regarding preservation of information related to these matters and investigations," they added, in letter sent to officials including Whitaker, White House Counsel Pat Cipollone and FBI Director Christopher Wray.

Nadler and other Democrats on the House Judiciary Committee also sent letters to Whitaker and the top Republican on the committee, retiring Rep. Bob Goodlatte, demanding "emergency" hearings on Sessions' ouster and replacement with Whitaker. Nadler and other Democrats on the committee suggested the shakeup appears to be an effort to alter oversight of special counsel Robert Mueller's probe in a way that favors the president. Republicans still control the committee schedule until January, so Democrats can't schedule hearings on their own until then.

"The forced firing of Attorney General Sessions appears to be part of an ongoing pattern of behavior by the President seeking to undermine investigation into Russian interference in the 2016 presidential election," House Judiciary Committee Democrats said in their letter.

Cummings, whose role on the key oversight committee puts him in a unique position to investigate Sessions' departure, said in a statement Wednesday that "Congress must now investigate the real reason for this termination, confirm that Acting Attorney General Matthew Whitaker is recused from all aspects of the Special Counsel's probe, and ensure that the Department of Justice safeguards the integrity of the Mueller investigation."

The Justice Department has declined to answer whether ethics officials have been asked to review if Whitaker should recuse himself from the Mueller probe. It's not clear whether his connections to Sam Clovis, who if friends with Whitaker and has been questioned in the Mueller probe, and with the president would be enough to force his recusal.

Counselor to the president Kellyanne Conway suggested on Thursday morning that the question of whether Whitaker will recuse himself is absurd.

"Well I don't know why he'd be recused. I'm not recused, you're not recused," Conway told reporters.

Sessions' departure — although not entirely unanticipated — came just hours after the midterm elections. As CBS News has reported, chief of staff John Kelly called Sessions shortly before a presidential press conference on Wednesday and asked him to resign.

In addition to Sessions' ouster, Democrats are also interested in looking into Mr. Trump's tax returns, and international business dealings.