WASHINGTON — Richard Grenell’s tenure as the nation’s top intelligence official may be short-lived, but he wasted no time this week starting to shape his team of advisers, ousting his office’s No. 2 official — a longtime intelligence officer — and bringing in an expert on Trump conspiracy theories to help lead the agency, according to officials.
Mr. Grenell has also requested the intelligence behind the classified briefing last week before the House Intelligence Committee where officials told lawmakers that Russia was interfering in November’s presidential election and that President Vladimir V. Putin of Russia favored President Trump’s re-election. The briefing later prompted Mr. Trump’s anger as he complained that Democrats would use it against him.
Joseph Maguire, the former acting director of national intelligence, and his deputy, Andrew P. Hallman, resigned on Friday. Mr. Grenell told Mr. Hallman, popular in the office’s Liberty Crossing headquarters, that his service was no longer needed, according to two officials. Mr. Hallman, who has worked in the office or at the C.I.A. for three decades, expressed confidence in his colleagues in a statement but also referred to the “uncertainties that come with change.”
The ouster of Mr. Hallman and exit of Mr. Maguire, who also oversaw the National Counterterrorism Center, allowed Mr. Grenell to install his own leadership team.
One of his first hires was Kashyap Patel, a senior National Security Council staff member and former key aide to Representative Devin Nunes, Republican of California and the former chairman of the House Intelligence Committee. Mr. Patel will have a mandate to “clean house,” CBS News reported, citing a person close to the matter.
Mr. Patel was best known as the lead author of a politically charged memo two years ago that accused F.B.I. and Justice Department leaders of abusing their surveillance powers to spy on a former Trump campaign adviser. The memo was widely criticized as misleading, though an inspector general later found other problems with aspects of the surveillance.
Working with Mr. Nunes, Mr. Patel began what they called Objective Medusa to examine the F.B.I.’s investigation into whether anyone associated with the Trump campaign conspired with Russia’s election interference in 2016.
“I hired him to bust doors down,” Mr. Nunes told the author Lee Smith for his book “The Plot Against the President,” which chronicles Mr. Patel’s investigations on behalf of the Republicans on the House Intelligence Committee. Mr. Patel was interviewed extensively in the book, which claims without proof that journalists, diplomats, law enforcement and intelligence officials engaged in a vast plot to undermine Mr. Trump’s campaign and then bring him down as president.
As acting director of national intelligence, Mr. Grenell has access to any secrets he may want to review. And he has requested access to information from the C.I.A. and other intelligence agencies, according to two people familiar with the matter.
The revelations about last week’s briefing reignited fears about Russia’s continuing efforts to interfere in the American election, including in the Democratic primary races.
During the briefing, which was supposed to focus on coordination between government agencies to fight election interference, not the acts themselves, Republicans challenged the intelligence agencies’ conclusion that the Russians continue to favor Mr. Trump. Some officials said the briefing was not meant to be controversial and that intelligence officials intended to simply reiterate what they had told the Senate Intelligence Committee weeks earlier.
Intelligence officials have already documented instances of the Kremlin trying to influence American politics, namely attempts by Russian military intelligence officers to hack into the Ukrainian energy company that once employed the son of former Vice President Joseph Biden Jr. Officials want to know whether the breach was an effort to help Mr. Trump, whose efforts to persuade Ukraine to announce investigations into Mr. Biden helped prompt his impeachment.
And during the congressional impeachment hearings, Fiona Hill, a former senior White House official who worked on Russia issues, warned about Moscow’s continued efforts to spread disinformation.
Mr. Trump himself wrote in a January letter accompanying the administration’s national counterintelligence strategy that “Russia remains a significant intelligence threat to United States interests — employing aggressive acts to instigate and exacerbate tensions and instability in the United States, including interfering with the security of our elections.”
Intelligence officials were scheduled to brief the full House and Senate on election security on March 10, arrangements that were made weeks ago, accounting to congressional aides.
How long Mr. Grenell will be able to stay as the acting director is an open question. For him to remain past March 11 — a limit imposed by federal law — Mr. Trump must formally nominate someone else for the director of national intelligence post.
Mr. Trump told reporters late Thursday that he was considering Representative Doug Collins of Georgia, the top Republican on the intelligence committee, but Mr. Collins took himself out of the running the next morning.
Mr. Collins, who helped lead the president’s impeachment defense, had received no advance notice that he was under consideration for the top intelligence post. He saw no reason to entertain a job he did not want, especially as he wages a special election battle for a Senate seat in his home state of Georgia.
“I know the problems in our intelligence community, but this is not a job that interests me at this time,” Mr. Collins said on Fox Business. “It’s not one that I would accept because I’m running a Senate race.”
People close to Mr. Collins have speculated that the president might have been trying to entice Mr. Collins out of that election to tamp down a messy intraparty fight that could cost Republicans control of the seat. Party leaders have converged around Senator Kelly Loeffler since Gov. Brian Kemp of Georgia appointed her to fill the state’s vacant Senate seat late last year and have made no secret of their disdain for Mr. Collins’s refusal to exit the race.
A nomination to a cabinet-level position would have required Mr. Collins to drop out of the race. But given his lack of intelligence experience and political track record, there was little likelihood the Senate would have confirmed him to the post.
With Mr. Collins off the table, Mr. Trump will need another potential nominee. The White House is considering Pete Hoekstra, the former Republican congressman who is now the American ambassador to the Netherlands, according to three officials.
Whether the Senate would be willing to formally consider Mr. Hoekstra is unclear. But if Mr. Trump were to send a nomination to the Senate it would, under federal law, allow Mr. Grenell to serve for at least another six months.
In a statement praising Mr. Maguire and Mr. Hallman, Senator Richard M. Burr of North Carolina, the chairman of the Senate Intelligence Committee, made no reference to Mr. Grenell.
On Friday, questions arose about Mr. Grenell’s past employment after ProPublica reported that he had done work for a Moldovan oligarch named Vladimir Plahotniuc who was banned from entering the United States because of his involvement in significant corruption.
Mr. Grenell wrote articles defending Mr. Plahotniuc but did not disclose he had been paid for his work, ProPublica reported. A lawyer speaking on Mr. Grenell’s behalf said he was not required to register with the Justice Department because he was not working at the direction of a foreign power.
David E. Sanger contributed reporting from Washington, and Maggie Haberman from New York.