Two senior Republicans have joined Democrats, legal experts, and lawmakers in expressing concern about the future of the Mueller probe after Trump asked Attorney General Jeff Sessions to resign.

Matthew Whitaker, who has criticized the investigation and is seen as a Trump loyalist, will oversee the probe as he serves as acting attorney general.

Mitt Romney and Susan Collins sounded the alarm and said the investigation must be allowed to continue without interference.



Hundreds of protests are scheduled across the US on Thursday to demand that Whitaker recuse himself from overseeing the investigation.



Bipartisan, national dread has set in over the fate of the Mueller probe into Russian meddling in the 2016 presidential election after President Donald Trump announced that Attorney General Jeff Sessions would be replaced by a Trump loyalist.

Matthew Whitaker will serve as acting attorney general and will assume oversight over the Russia investigation and Special Counsel Robert Mueller from Deputy Attorney General Rod Rosenstein.

Sessions, who would have been in charge, had recused himself due to his involvement in Trump's 2016 campaign, much to Trump's disappointment.

Members of both parties, as well as lawmakers and legal experts, expressed concerned as Whitaker is widely seen as a Trump loyalist who has previously criticized Mueller's investigation.

Senior members of Trump's own party have sounded the alarm, saying that the investigation must be allowed to continue after Trump requested that Sessions stand down and repeatedly criticized Sessions' handling of the probe.



Read more: Jeff Sessions resigns as attorney general at Trump's request

Mitt Romney, a former Republican presidential candidate who was elected as a Utah Senator on Tuesday, tweeted: "It is imperative that the important work of the Justice Department continues, and that the Mueller investigation proceeds to its conclusion unimpeded."

Maine Senator Susan Collins, also a Republican, said she was "concerned" that Rosenstein would no longer be overseeing the probe.



"It is imperative that the Administration not impede the Mueller investigation … Special Counsel Mueller must be allowed to complete his work without interference."



Whitakter wrote for CNN last year that the special counsel was "going too far" and needed to be brought under control.

He said that Trump was "absolutely correct" that the investigation should not look at the president's finances. "Mueller has come up to a red line in the Russia 2016 election-meddling investigation that he is dangerously close to crossing."

Congressional Republicans had warned Trump in March against trying to interfere with the probe or fire Mueller.



Read more: Richard Nixon's White House counsel says Jeff Sessions' ousting 'like a planned murder'

A Justice Department trial attorney told The Daily Beast that Whitaker "is on record as being more interested in propping up Trump than in upholding the rule of law.



"It’s hard to have confidence that he’ll do anything other than what the president had said in his tweets."

Democrats have raised concerns over the future of the investigation, with Senate Minority Leader Chuck Schumer saying that Session's departure puts the investigation in "new and immediate peril."



Read More: A former federal prosecutor thinks Mueller's quiet period before the midterms may not have been so quiet after all

Legal experts and lawmakers have also sounded the alarm.

Jens David Ohlin, a vice dean at Cornell Law School and an expert in criminal law, told Business Insider that it was a "disturbing development."



"The nation's eyes are on Mr. Whitaker and how he discharges his responsibility to oversee the Mueller investigation."

Hundreds of protests are scheduled across the US on Thursday to demand that Whitaker recuse himself immediately from overseeing the investigation.