Acting FBI director Andrew McCabe on Thursday rejected the Trump White House’s characterization of the Russian meddling probe as a low priority and delivered a passionate defense of former director James B. Comey — putting himself squarely at odds with the president while the bureau’s future hangs in the balance.

McCabe, who had been the No. 2 official in the FBI until President Trump fired Comey this week, said that the bureau considered the probe of possible coordination between the Kremlin and the Trump team during the 2016 election campaign a “highly significant investigation” and that it would not be derailed because of a change in leadership.

“You cannot stop the men and women of the FBI from doing the right thing, protecting the American people and upholding the Constitution,” McCabe said.

[Furor over Comey firing grows with news that he sought resources for Russia investigation before his dismissal]

McCabe’s assertion, which came during a hearing before the Senate Intelligence Committee, directly contradicted a White House spokeswoman’s description of the Russian case as “probably one of the smallest things that they’ve got going on their plate.”

McCabe also promised that if the White House tried to interfere in the bureau’s work, he would alert the committee, and he said he would not offer any status updates about the matter to the president or those who work for him. McCabe said there had “been no effort to impede our investigation to date.”

The hearing was supposed to have been one at which Comey appeared with other top U.S. intelligence officials to discuss threats to the United States across the globe. But after Comey was fired Tuesday and McCabe was chosen to fill his seat, the discussion of threats turned largely to Russia and the integrity of the FBI.

McCabe is not even certain to remain as the FBI’s acting director. He was elevated to the post essentially by default, and on Wednesday, Attorney General Jeff Sessions and Deputy Attorney General Rod J. Rosenstein interviewed four candidates to find someone potentially to take over in the short term. It is also possible that McCabe could stay on.

Ultimately, Trump will have to nominate a permanent replacement, and that person will have to undergo the Senate confirmation process.

McCabe did not seem concerned with winning Trump’s favor. Asked by Sen. Ron Wyden (D-Ore.) whether he would “refrain” from providing “updates to the president or anyone else in the White House on the status of the” Russia probe, McCabe said unequivocally, “I will.”

That was noteworthy, because just hours after McCabe’s testimony ended, NBC News published portions of an interview with Trump in which the president claimed that Comey had told him three times that he was not under investigation — at least once in a phone call that Trump initiated.

“I said, ‘If it’s possible would you let me know am I under investigation?’ [Comey] said, ‘You are not under investigation,’ ’’ Trump said in the interview.

(Jason Aldag,Sarah Parnass/The Washington Post)

The claim — which Trump also made in his letter firing Comey — could not immediately be verified, and McCabe declined to speak about it.

McCabe also rejected the president’s assertions that Comey “was not doing a good job” and that the bureau was “in turmoil.” McCabe acknowledged that there were some in the agency who were “frustrated with the outcome” of the investigation of Hillary Clinton’s use of a private email server while she was secretary of state — the handling of which was cited as a rationale for firing Comey.

But McCabe defended leadership at the bureau and praised Comey, in particular.

“It has been the greatest privilege and honor of my professional life to work with him,” McCabe said of Comey. “Director Comey enjoyed broad support within the FBI and still does to this day.”

White House principal deputy press secretary Sarah Huckabee Sanders later disputed that assertion.

“I have heard from countless members of the FBI that are grateful on the president’s decision, and we may have to agree to disagree,” Sanders said.

McCabe was joined at the hearing by virtually every other top official whose job it is to detect and prevent Russian spy operations. The others on the witness list were CIA Director Mike Pompeo; Director of National Intelligence Daniel Coats; the National Security Agency’s director, Mike Rogers; National Geospatial-Intelligence Agency Director Robert Cardillo; and the Defense Intelligence Agency’s director, Vincent Stewart.

The Senate Intelligence Committee, like the FBI, is investigating alleged Russian meddling in the 2016 presidential election campaign, and its chairman and vice chairman announced Wednesday that they had issued a subpoena to former national security adviser Michael Flynn for documents related to that investigation.

Flynn resigned from the Trump White House after news reports on potentially illegal contacts with the Russian ambassador to the United States, which acting attorney general Sally Yates warned might make Flynn susceptible to blackmail. He also has faced scrutiny for payments he received from Russian-backed entities, including the RT television network.

The bureau’s probe, the only one that could produce criminal charges, is separate from the committee’s, and lawmakers on both sides of the aisle feared that it might be upended now that Comey is gone. Many have called for a special counsel to be appointed; Rep. Mike Coffman (R-Colo.) became the latest to do so, in a statement issued Thursday. McCabe asserted that the bureau’s independence had not been compromised.

“Do you need somebody to take this away from you and somebody else to do it?” Sen. James Lankford (R-Okla.) asked.

“No, sir,” McCabe responded.

McCabe did not definitively resolve a dispute over whether Comey asked Rosenstein for more resources for the Russia investigation last week, although he asserted that the bureau had “resourced that investigation adequately.” Democrats have said that Comey informed lawmakers of such a request, but the Justice Department has denied that one was made.

McCabe said he was “not aware of that request, and it’s not consistent with my understanding of how we request additional resources.”

As the deputy director of the FBI, McCabe would have been intimately involved in the Russia investigation even before Comey’s firing. He was notably at the center of a February incident in which the White House reportedly enlisted senior members of the intelligence community and Congress in efforts to counter news reports about Trump associates’ ties to Russia.

CNN reported at the time that the FBI had refused administration requests to knock down media reports on the subject, and the administration fired back with a claim that McCabe had pulled aside White House Chief of Staff Reince Priebus to tell him a New York Times story was “B.S.”

McCabe was also at the center of a controversy in the Clinton email investigation — the case that administration officials have pointed to as Trump’s basis for firing Comey. The Justice Department inspector general is investigating whether McCabe should have been recused from the case because his wife ran for a Virginia Senate seat and took money from the political action committee of Virginia Gov. Terry McAuliffe (D), a Clinton ally.

The FBI asserted at the time that McCabe had checked with ethics officials and followed agency protocols. He also was not yet deputy director when his wife was recruited to run.

Amber Phillips contributed to this report.

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