In this July 13, 2018 photo, Attorney General Jeff Sessions speaks in Portland, Maine. (AP Photo/Robert F. Bukaty, File)

WASHINGTON — The future of the special counsel investigation into Russian interference in the 2016 campaign was thrown into uncertainty Wednesday after President Donald Trump ousted Attorney General Jeff Sessions, a move that will result in a change in the probe’s supervision.

Trump named as acting attorney general Matthew Whitaker, Sessions chief of staff, who as a legal commentator last year wrote that special counsel Robert Mueller III appeared to be taking his investigation too far.

Special Counsel Robert Mueller leaves a meeting with members of the Senate Judiciary Committee in Washington on June 21, 2017. (Eric Thayer/Bloomberg)

A Justice Department official said Wednesday that Whitaker would assume final decision-making authority over the special counsel probe instead of Deputy Attorney General Rod Rosenstein.

Since last year, Rosenstein has overseen the investigation because Sessions, a key Trump surrogate in 2016, recused himself from dealing with matters involving the campaign. It wasn’t immediately clear what role, if any, Rosenstein may play in the probe going forward.

As the ultimate supervisor of the investigation, Whitaker could sharply curtail Mueller’s authority, cut his budget or order him to cease lines of inquiry.

However, Whitaker’s role could still be reviewed by ethics officials. Comments he has made about Mueller’s investigation could put pressure on him to recuse himself, as Sessions did.

A legal commentator before he came into the Justice Department, Whitaker has mused publicly about how a Sessions replacement might reduce Mueller’s budget “so low that his investigation grinds to almost a halt.”

He wrote in a September 2017 column that Mueller had “come up to a red line in the Russia 2016 election-meddling investigation that he is dangerously close to crossing” after CNN reported that the special counsel could be looking into Trump and his associates’ financial ties to Russia.

Some Democrats immediately called for Whitaker to recuse himself from supervision of the investigation, including Sen. Minority Leader Charles Schumer, N.Y.

Sen. Mark Warner, D-Va., the ranking member of the Senate Intelligence Committee, which has also been investigating the 2016 election, said in a statement that any effort to interfere in Mueller’s investigation would be a “gross abuse of power by the President.”

“While the President may have the authority to replace the Attorney General, this must not be the first step in an attempt to impede, obstruct or end the Mueller investigation,” Warner said.

Trump’s decision to push Sessions out Wednesday conflicted with comments he offered during a news conference on Wednesday when he insisted he had a right to end the investigation but said that he would prefer to “let it go on.”

“I could fire everybody right now, but I don’t want to stop it because politically I don’t like stopping it,” Trump said. “It’s a disgrace. It should never have been started, because there is no crime.”

Whitaker has not been confirmed by the Senate and, by law, can only serve for 210 days before he must be replaced by someone who has been confirmed.

He will take over the investigation at a particularly critical moment, as Mueller was expected to end what has been a quiet public phase of his investigation.

In the run-up to Election Day, there were no indictments or public pronouncements by the special counsel’s office, in keeping with Justice Department guidelines that prosecutors should avoid taking steps that could be perceived as intending to influence the outcome of the vote.

With the midterm elections now over, Mueller faces key decision points in his 18-month-old investigation into Russian interference in the 2016 campaign – a probe that has already led to charges against 32 people, including 26 Russians. Four aides to President Trump have pleaded guilty to various charges, most recently his former campaign chairman Paul Manafort in September.

Among the most pressing matters now before the special counsel: a probe into longtime Trump adviser Roger Stone’s activities and ongoing negotiations with Trump’s legal team over a request to interview him.

For months, Mueller has been seeking to question Trump as part of his investigation, which is also examining whether the president has sought to obstruct the probe.

Jacob Frenkel, a former state and federal prosecutor who is now in private practice at Dickinson Wright, noted that by keeping a low profile, Mueller avoided the widespread criticism that then-FBI Director James B. Comey faced when he made announcements about an investigation into Democratic nominee Hillary Clinton’s email practices in the final weeks of the 2016 race.

But Frenkel said he did not expect Mueller’s silence to continue for long.

“For me, the question is, ‘How many indictments and who?'” Frenkel said. “It is not an ‘if.’ ”

A spokesman for Mueller declined to comment.

Mueller’s prosecutors have already laid out detailed allegations of how Russia sought to manipulate Americans through social media, break into state voting systems and hack the email accounts of Democratic committees and party leaders.

But the special counsel’s team has not indicated publicly that it has drawn any conclusions about whether Trump associates conspired with the Russians or whether the president obstructed justice.

At some point, the special counsel is expected to issue a confidential report to Rosenstein containing his conclusions about both matters.

Those findings – which could be shared with Congress – are eagerly awaited by Democrats, who on Tuesday regained control of the House. Minority Leader Nancy Pelosi, D-Calif., has said that Mueller’s conclusions will affect whether the party pursues impeachment proceedings against Trump.

Barbara McQuade, a former U.S. attorney for the Eastern District of Michigan, said there have been some signs that Mueller may be wrapping up. She noted that he has shed staff members and handed off investigations to prosecutors in New York and Washington.

But, she added, it is difficult to predict when Mueller might conclude the probe. If Stone or others were to be charged, McQuade said, Mueller might spend time trying to persuade them to cooperate and then use the information they provide to chase new leads.

“It seems that the end is in sight,” she said, “but I don’t know whether that is a matter of weeks or months.”

Behind the scenes, Mueller’s investigators have been intensively gathering evidence and questioning witnesses in recent weeks.

The grand jury hearing evidence in the Russia investigation has been seen meeting at a federal courthouse in Washington on six of the last eight Fridays.

Based on witnesses who have been called to the grand jury, the special counsel appears to be intensely focused on Stone.

The longtime Trump friend and former adviser is under scrutiny for claims he made in the 2016 campaign that suggested he was in contact with WikiLeaks. In the final months of the White House race, the group published Democratic emails that prosecutors allege were hacked by Russian military operatives.

Stone has repeatedly maintained that he was not in touch with WikiLeaks and did not have advance knowledge of its plans. He said he based his comments on publicly available interviews with WikiLeaks founder Julian Assange and tips from associates, including New York comedian and radio host Randy Credico, who interviewed Assange on his program in August 2016.

Credico has denied serving as a back-channel to Assange for Stone.

In recent weeks, two more Stone associates testified before the grand jury – among at least nine people connected to Stone who have been contacted by prosecutors so far.

Filmmaker David Lugo and lawyer Tyler Nixon both told The Washington Post last month that Credico acknowledged to them that he gave Stone information from Assange. Lugo, who appeared before the grand jury Oct. 19, said he turned over text messages and emails to Mueller’s team. Nixon said he testified last week.

Separately, conservative writer Jerome Corsi was interviewed by investigators over three days last week and appears to be emerging as a key witness in the Mueller investigation into Stone’s activities.

In an appearance on his live-streamed Internet show Monday, Corsi told viewers that he has been in near-continuous contact with Mueller’s team in recent weeks.

“It’s been two months, on a really constant basis in the Mueller investigation. It’s been one of the biggest pushes of my life,” said Corsi, who added that he could provide no specifics of his interactions with Mueller.

David Gray, an attorney for Corsi, declined to comment.

Mueller faces significant legal battles in the coming weeks.

Andrew Miller, a longtime aide to Stone, has refused to comply with a subpoena to appear before the grand jury, arguing that Mueller’s probe is unconstitutional. A judge has held him in contempt but stayed that ruling until the matter is resolved. A hearing is scheduled for Thursday.

Meanwhile, the special counsel must decide whether to accept only written answers from the president or to fight for an interview. Such a move would likely require issuing a subpoena to the president, which would then draw a legal challenge from Trump’s team.

By mid-November, the president’s attorneys plan to turn over Trump’s written answers to roughly a dozen questions the special counsel has posed – including the president’s knowledge of the hacked Democratic emails and his advisers’ contacts with Russians during the campaign and transition, according to two people familiar with the decision.

In September, after eight months of negotiations over a possible interview with Trump, the two sides agreed that Mueller would accept written answers to a subset of questions as a partial first step.

The president’s answers have not been completed yet, according to the people, in part because his attorneys had trouble getting time with Trump amid a series of crises, including the death of Washington Post contributing columnist Jamal Khashoggi, the mailing of pipe bombs to Democratic leaders, and a fatal shooting at a Pittsburgh synagogue.

Trump’s legal team has repeatedly resisted Mueller’s request for a sit-down interview with the president since he first proposed it in December 2017. But they have never flatly rejected it.

Trump attorney Rudy Giuliani has said he opposes the idea of the interview, worried that Mueller would accuse Trump of perjury. The president – who once voiced eagerness to set the record straight – is now cool to the notion of speaking to the special counsel, according to people familiar with his views.

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The Washington Post’s Devlin Barrett, Spencer S. Hsu, Manuel Roig-Franzia and Philip Rucker contributed to this report.