The acting director of the National Security Agency tried to protect one of his top scientists from losing his security clearance as Tulsi Gabbard, the director of national intelligence, prepared to announce the move this week, according to officials briefed on the matter.
The effort failed. Ms. Gabbard, on orders from President Trump, fired the scientist, who was a leading government expert on artificial intelligence, cryptology and advanced mathematics.
The scientist, Vinh Nguyen, was one of 37 current and former national security officials whose security clearances were revoked on Tuesday. Many, though not all, had tangential connections to the intelligence agencies’ review of Russian efforts to influence and meddle in the 2016 election.
Ms. Gabbard has released documents about that intelligence inquiry and accused Obama administration officials of related crimes, an effort Mr. Trump has praised.
Lt. Gen. William J. Hartman, the acting N.S.A. director, called Ms. Gabbard in the days before the revocation and asked to see the evidence that Mr. Nguyen, the agency’s chief data scientist, had done anything that merited the revocation of his security clearance.
Ms. Gabbard rebuffed the request, the officials said. The list of people losing their clearance began to circulate Tuesday morning and was made public in the afternoon.
The N.S.A. referred all questions to Ms. Gabbard’s office, which did not return a request for comment.
Former officials have criticized the revocation of the 37 security clearances and the wider purge of national security officials. In an article in The Atlantic published on Wednesday, William J. Burns, the former C.I.A. director and a longtime diplomat, said the removal of public servants was part of a campaign of retribution.
“It is about breaking people and breaking institutions by sowing fear and mistrust throughout our government,” Mr. Burns wrote. “It is about paralyzing public servants — making them apprehensive about what they say, how it might be interpreted, and who might report on them. It is about deterring anyone from daring to speak truth to power.”
Mr. Nguyen, the son of a South Vietnamese general who fought alongside American forces in the Vietnam War, was recruited as a 17-year-old high school student to join the National Security Agency because of his math skills.
He rose through the ranks of the agency to become its chief data scientist. Friends and former colleagues of Mr. Nguyen said he had been in charge of developing artificial intelligence systems to improve the gathering of foreign communications. He has also been involved in the intelligence community’s work on quantum computing, which has the potential to break current encryption systems and revolutionize espionage.
In the days before Mr. Nguyen was dismissed, N.S.A. officials were concerned that his job was at risk, as conservative publications began to look at his work as the national intelligence officer in charge of cyber in 2016.
Reports in conservative publications had led to the ouster of the N.S.A.’s top lawyer, April Falcon Doss, in July. And the previous director of the agency, Gen. Timothy D. Haugh, was fired in the spring after Laura Loomer, the far-right conspiracy theorist, accused him of having ties to Gen. Mark Milley, the former chairman of the Joint Chiefs of Staff.
Former officials had expected General Hartman, who replaced General Haugh, to be nominated for the job permanently. But neither the Pentagon nor the White House has formally made that move.