The ongoing investigation has produced guilty pleas from four former Trump aides.
Separately, Justice Department prosecutors in NY secured a guilty plea from Trump's former personal lawyer, Michael Cohen, who said the president directed him to arrange hush money payments before the 2016 election to two women who said they had sex with Trump. "Special Counsel Mueller must be allowed to complete his work without interference-regardless of who is AG".
Whitaker, a former USA attorney from Iowa who twice ran unsuccessfully for statewide office and founded a law firm with other Republican Party activists, once opined about a scenario in which Trump could fire Sessions and then appoint an acting attorney general who could stifle the funding of Mueller's probe.
Trump has continued pressing his view that Mueller leads a team staffed by Democrats operating under an illegal mandate.
Protests took place around the country, including in Virginia Beach, in response to President Trump's firing of Jeff Sessions as Attorney General.
In addition to Mueller's subpoena of the Trump Organisation, an umbrella company that encompasses Trump's business ventures, federal prosecutors in Manhattan indicted the president's former lawyer, Michael Cohen, for campaign finance fraud related to payments made on behalf of Trump.
Donald Trump with Mr Sessions in December a year ago.
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But, as it turns out, she was pretty upbeat about all of them. "Wish I could say 'thank you " to Malcolm, cause he was an angel. The singer of 25 years has also stopped the operation of his last album, Sweetener and has just unveiled a brand new song .
In February 2016, Sessions became the first sitting senator to endorse Trump's presidential campaign, and in the months leading up to the election, he became one of the candidate's closest national security advisers.
He served as the U.S. attorney in the state's southern district, was elected state attorney general in 1994 and then to the Senate in 1996. 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.
Protesters' demands include having Whitaker recuse himself from overseeing Mueller's investigation, and for Congress to protect the probe with legislation. "Trump's ouster of AG Sessions and replacing him with Trump toady Matthew Whitaker is clearly a move to interfere with the investigation of Russia's attack on the 2016 election".
Can Whitaker be forced to recuse himself?
In July 2017 Mr Trump told the New York Times: "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".
In pushing out his attorney-general, the President cast aside one of his earliest and strongest supporters.
Trump has long expressed frustration with Sessions over his recusal from the Justice Department's Russian Federation investigation.