Donald Trump moved to impede the Russia investigation on Wednesday by replacing Attorney General Jeff Sessions with a temporary successor, Matthew Whitaker, who argued last year that Special Counsel Robert Mueller should be barred from investigating the president’s finances.

By naming Whitaker, who has been serving as Sessions’s chief of staff, as the acting attorney general, Trump effectively appointed the former federal prosecutor to oversee the investigation into his 2016 campaign’s contacts with Russia, taking that responsibility away from Deputy Attorney General Rod Rosenstein, who appointed Mueller after Sessions had recused himself from the matter.

Before he joined the Justice Department, Whitaker had argued last year in his role as a CNN legal analyst that the Mueller investigation needed to be reined in, writing in an opinion piece that “investigating Donald Trump’s finances or his family’s finances falls completely outside of the realm of his 2016 campaign and allegations that the campaign coordinated with the Russian government or anyone else. That goes beyond the scope of the appointment of the special counsel.”

“The Trump Organization’s business dealings are plainly not within the scope of the investigation, nor should they be,” Whitaker added in that August 6, 2017, op-ed. Referring to reports at the time that the special counsel probe had widened to focus on possible financial crimes, unconnected to the 2016 election, Whitaker wrote that it was time for the Justice Department “to order Mueller to limit the scope of his investigation.”

Whitaker also downplayed the importance of the investigation in a series of appearances on CNN in 2017. In July of that year, he argued that the 2016 Trump Tower meeting between a lawyer connected to the Russian government and Donald Trump’s oldest son, Don Jr., his son-in-law, Jared Kushner, and his campaign manager, Paul Manafort, was not evidence of collusion.

The same month, he said that while the promised dirt on Hillary Clinton offered by Russian friends of the Trumps turned out to be a “ludicrous” conspiracy theory about Russian funding of the Democrats, there was nothing improper about the campaign agreeing to the meeting. In politics, Whitaker said, “you would always take that meeting.”

In another appearance the same month, Whitaker suggested that Trump could force Sessions out and replace him with an acting attorney general who would then have the power to hamper the special counsel by cutting the funding for his investigation.

“I could see a scenario where Jeff Sessions is replaced,” Whitaker said, “and that attorney general doesn’t fire Bob Mueller, but he just reduces his budget to so low that his investigation grinds to almost a halt.”

On Twitter in 2017, Whitaker also disparaged the Mueller investigation as a “lynch mob.”

Trump’s “Wednesday afternoon massacre” alarmed Democrats, including Sen. Tim Kaine of Virginia, and Sally Yates, a former acting attorney general who was fired by Trump after she refused to defend his Muslim ban in court.

As the Washington Post correspondent Robert Costa noted, Whitaker is a friend and former political ally of one of the witnesses in the Mueller probe, Sam Clovis, a Trump campaign aide who had encouraged another advisor, George Papadopoulos, to travel to Russia and meet with Russian officials in August, 2016.

“We’re currently friends,” Clovis said of Whitaker in an interview with The Post on Wednesday. “I texted him congratulations today.”

Clovis also told Talking Points Memo on Wednesday that Whitaker had served as an informal advisor on his work for the Trump campaign. “He and I are very good friends, very close friends,” Clovis said. “He’ll fit right into this, he’ll be a great acting Attorney General.”

During the 2016 campaign, Whitaker, a former United States attorney, argued in an opinion piece that he would have prosecuted Hillary Clinton for using a private email server when she served as secretary of state. “According to FBI Director James Comey’s statement,” Whitaker wrote on July 5, 2016, “former secretary of State Hillary Clinton could have been charged with violating several different code sections, and he detailed the evidence that supports bringing criminal charges.”

“Yet, Director Comey’s judgment was that ‘no reasonable prosecutor’ would bring the case,” Whitaker added. “I disagree.”

Several Democratic senators, including Chris Coons of Delaware and Kamala Harris of a California, a possible contender for her party’s 2020 presidential nomination, called for Whitaker to recuse himself from oversight of the Mueller investigation.

Given that he was appointed by a president who is already under investigation for obstructing justice by firing Comey, and has not been confirmed by the senate, some legal experts suggested that Whitaker might not have the legal authority to oversee the special counsel’s work.

One of them, Neal Katyal, a former acting solicitor general in the Obama administration, pointed out that Clarence Thomas had ruled recently that such an appointee could not exercise those powers.

The Democratic activist group MoveOn announced nationwide protests on Thursday to defend the Mueller investigation.

Updated: Wednesday, Nov. 7, 6:10 p.m. Eastern Time
This report was updated with more reaction to Matthew Whitaker’s appointment as acting attorney general.