In the aftermath of the midterm elections, in which Democrats took control of the House of Representatives, Mr Trump ousted Mr Sessions and replaced him with Matthew Whitaker, a Trump loyalist who has previously been critical of the special counsel investigation into whether the Trump campaign colluded with Russia.
Democrats said they feared the decision to appoint Mr Whitaker was the prelude to a decision by Mr Trump to terminate the investigation by Mr Mueller, which the president has constantly described as a “witch hunt”.
While most Republicans remained silent about the firing of Mr Sessions – among them South Carolina senator Lindsey Graham, who said last year there would be “hell to pay” if the attorney general was got rid off – three senior members of the party urged Mr Trump to allow Mr Mueller complete his probe.
Mitt Romney, who challenged Barack Obama for the White House in 2012, and who this week was elected to the senate from Utah, wrote on Twitter: “I want to thank Jeff Sessions for his service to our country as attorney general.
He added: “Under acting attorney general Matthew Whitaker, it is imperative that the important work of the Justice Department continues, and that the Mueller investigation proceeds to its conclusion unimpeded.”
Susan Collins, the Republican senator from Maine, and one of the party’s more moderate elected politicians, also praised Mr Sessions, saying he was “a leader of integrity who served our country well”.
“It is imperative that the administration not impede the Mueller investigation,” she said. ”I’m concerned Rod Rosenstein will no longer be overseeing the probe. Special Counsel Mueller must be allowed to complete his work without interference – regardless of who is AG.”
Lamar Alexander, Republican senator from Tennessee, issued perhaps the stormiest warning, saying the Senate would not confirm an attorney general who sought to stop the Russia probe.
I want to thank Jeff Sessions for his service to our country as Attorney General. Under Acting Attorney General Matthew Whitaker, it is imperative that the important work of the Justice Department continues, and that the Mueller investigation proceeds to its conclusion unimpeded.
— Mitt Romney (@MittRomney) November 7, 2018
But those three were the only senior Republicans to speak out. Senator Graham, who offered fierce defence of both Mr Sessions, and Mr Mueller’s probe just 12 months ago, was criticised for merely saying: “I look forward to working with President Trump to find a confirmable, worthy successor so that we can start a new chapter at the Department of Justice and deal with both the opportunities and challenges our nation faces.”
Newly emboldened Democrats have said any attempt to terminate Mr Mueller’s investigation would amount to a constitutional crisis.