WASHINGTON — The future of the special counsel investigation into Russian interference in the 2016 campaign was thrown into uncertainty Wednesday after President 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.
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 Senate minority leader Charles Schumer of New York.
Senator Mark Warner, Democrat of Virginia, 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 e-mail 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 e-mail 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, a California Democrat, has said that Mueller’s conclusions will affect whether the party pursues impeachment proceedings against Trump.