Trump installed Matt Whitaker, chief of staff at the Justice Department, as acting attorney general and put him in charge of the Russia probe led by Special Counsel Robert Mueller, according to a U.S. official. Whitaker, who has been a critic of the Russia probe, now has the power to fire Mueller or curb his investigation into Russian interference in the 2016 presidential campaign.

Trump said he will nominate a permanent successor for Sessions at a later date. Winning confirmation in the Senate may become easier because Republicans gained seats in Tuesday’s midterm elections.

Democrats warned against interference in the probe. Senate Minority Leader Chuck Schumer said that “protecting Mueller and his investigation is paramount.”

Mueller declined to comment, according to his spokesman, Peter Carr.

Before Trump gave a news conference on Wednesday, White House Chief of Staff John Kelly called Sessions and told him that Trump wanted him out, the official said.

Trump said at the news conference that he wanted the Mueller probe to end, calling it “very unfair.”

“It should end because it’s very bad for our country,” he said.

Deputy Attorney General Rod Rosenstein, who appointed Mueller and has overseen his probe from the beginning will stay in his post, according to the official.

Whitaker, a former U.S. attorney for the Southern District of Iowa, had served as Sessions’s chief of staff since September 2017. Previously he was a conservative legal commentator who was critical of the scope of Mueller’s probe.

In July 2017, he said during an interview on CNN that he could envision a scenario under which a temporary attorney general doesn’t fire Mueller but rather “just reduces his budget to so low that his investigations grinds to almost a halt.”

The next month, Whitaker wrote an op-ed posted on CNN’s website in which he argued that Mueller’s investigation appears to be going too far and may constitute a “witch hunt,” echoing one of Trump’s favorite descriptions to criticize and discredit the probe.

Democratic Representative Jerrold Nadler, who is in line to become chairman of the House Judiciary Committee in January, tweeted: “Americans must have answers immediately as to the reasoning behind @realDonaldTrump removing Jeff Sessions from @TheJusticeDept. Why is the President making this change and who has authority over Special Counsel Mueller’s investigation? We will be holding people accountable.”

Whitaker was U.S. attorney for the Southern District of Iowa from 2004 to 2009 under President George W. Bush.

Republicans warned Trump last year against replacing Sessions, but some of that resistance appeared to break down by late August, when several key GOP senators signaled to Trump that he could find a new attorney general after the midterm elections were safely past.

“The president’s entitled to an attorney general he has faith in, somebody that’s qualified for the job, and I think there will come a time, sooner rather than later, where it will be time to have a new face and a fresh voice at the Department of Justice,” Senator Lindsey Graham of South Carolina, who may be in line to head the Judiciary Committee next year, told reporters in August. “Clearly, Attorney General Sessions doesn’t have the confidence of the president.”

Sessions, a 71-year-old former Republican senator from Alabama, was the first senator to endorse Trump’s insurgent presidential campaign. But the former federal prosecutor went from being one of Trump’s closest campaign advisers to an outcast. Sessions had held on to his job as the nation’s top law enforcement officer despite frequent bursts of embarrassingly public criticism from Trump.

“I’m disappointed in the attorney general for many reasons,” Trump told reporters in September.

The president lambasted Sessions for recusing himself from decisions about the federal probe into Russian meddling, an inquiry the president has regularly lambasted as “fake news” and a “witch hunt.”

Sessions took himself out of decision-making on the probe in March 2017 even after Trump dispatched the White House lawyer to persuade him not to do so, according to a person familiar with the matter.

That left Rosenstein overseeing the investigation, and he named Mueller as special counsel. DM