In his telling, that bureaucracy, now run by his own appointees, is a nest of political saboteurs out to undermine him — an accusation that raised fears that he was tearing at the credibility of some of the most important institutions in American life to save himself.
“I can’t think of another time when this has happened,” said Jack L. Goldsmith, a Harvard law professor who headed the Justice Department’s Office of Legal Counsel under President George W. Bush. “And it’s happening largely because the president is being investigated.”
The attacks are having an impact. A new SurveyMonkey poll for Axios, a news website, released on Saturday showed that only 38 percent of Republicans have a favorable view of the F.B.I., compared to 64 percent of Democrats. In interviews, more than a dozen officials who work at or recently left the Justice Department and the F.B.I. said they feared that the president was mortgaging the credibility of those agencies for his own short-term political gain as he seeks to undercut the Russia inquiry led by the special counsel, Robert S. Mueller III.
“Thanks to this rhetoric, there is a subset of the public that won’t believe what comes out of the Mueller investigation,” said Christopher Hunter, a former F.B.I. agent and prosecutor who left the Justice Department at the end of last year. Mr. Hunter said he worried that juries might be more skeptical of testimony from agents even in criminal trials unrelated to Mr. Trump. “All it takes to sink a case,” he said, “is for one juror to disbelieve the F.B.I.”
Several career professionals said they had left recently after concluding that it was no longer possible to serve. “I felt that as a lawyer, I could serve the public interest and carry out public service better and more effectively from outside, at least on the issues I care about, than from inside the government,” said Joshua Geltzer, a former national security lawyer in the Justice Department. “There are others who feel similarly.”
For some, a siege mentality has taken hold. “Until recently, people in the department were in raised eyebrow mode,” said Sharon McGowan, a former principal deputy chief of the appellate section of the Civil Rights Division who left soon after the new administration took over. “But now they’re starting to get worried.”
Since taking office, Mr. Trump has assailed a number of major institutions in society, including Congress, the courts, the news media, intelligence agencies, Hollywood, professional sports and even his own party. But the attacks on law enforcement are tied up with his own political fate as investigators bear down.
The closest analogy historians summon is the Saturday Night Massacre in 1973, when President Richard M. Nixon ordered the firing of the Watergate prosecutor, and both the attorney general and his deputy resigned rather than comply, leaving it to the Justice Department’s No. 3 official to carry it out. Even then, Nixon was publicly targeting the prosecutor, not the institutions themselves.
Ever since, the notion of a president dismissing investigators looking at his own actions had been unthinkable in Washington — at least until Mr. Trump fired James B. Comey, the F.B.I. director, last year. President Bill Clinton’s surrogates relentlessly criticized Kenneth W. Starr, the independent counsel investigating him, but ousting him was never a viable option, and as much as Mr. Clinton detested Louis J. Freeh, the F.B.I. director at the time, he did not launch a sustained public attack on him or the agency.
Even before this past week, Mr. Trump had publicly assailed Attorney General Jeff Sessions for recusing himself from the Russia investigation and left open the possibility that he might even fire him. Last summer, Mr. Trump sought to fire Mr. Mueller, only to back down after the White House counsel threatened to resign, The New York Times reported last month. He also considered firing Mr. Rosenstein, who oversees Mr. Mueller.
“It’s scary when someone can use the forces of government for their own benefit, the way Nixon did and the way this president is now doing,” said Sidney Davidoff, a onetime adviser to Mayor John V. Lindsay of New York and one of 20 people on Nixon’s original enemies list. “As an attorney and as a private citizen, I’d like to believe that the investigatory agencies are doing a job for the American people, not at someone’s whim. It’s not a monarchy.”
Mr. Trump’s advisers dismiss such concerns as overwrought. They said the memo, drafted by Republicans led by Representative Devin Nunes of California, the Intelligence Committee chairman, and declassified by Mr. Trump, raised serious and legitimate questions about the way the F.B.I. used information gathered by a former spy paid by Mrs. Clinton’s campaign and the Democrats to help justify a warrant for surveillance on a former Trump campaign adviser tied to Russia.
Mr. Trump’s critics, his advisers argue, are turning a blind eye to government misconduct out of their own partisan animus toward the president. Neither the F.B.I. nor the Justice Department should be above questioning, they say, and Mr. Trump’s willingness to do so should not be taken as a slight against the vast majority of people who work there.
“The president has stated many times that he respects the rank and file of the F.B.I., the 25,000 men and women who do a great job there,” Kellyanne Conway, the president’s counselor, said on Fox News. “This particular investigation has taken a lot of twists and turns, and it’s led us to a few bad actors who had direct responsibility for an investigation about his political opponent who are obviously biased against him.”
Mr. Trump seized on the memo on Saturday to assert that it renders the Russia investigation moot. “This memo totally vindicates ‘Trump’ in probe,” he wrote on Twitter. “But the Russian Witch Hunt goes on and on. Their was no Collusion and there was no Obstruction (the word now used because, after one year of looking endlessly and finding NOTHING, collusion is dead). This is an American disgrace!”
For Mr. Trump, the memo represents the latest example of a secret document containing explosive information that shadowy, powerful figures do not want made public, like the famous long-form birth certificate that President Barack Obama was supposedly hiding to cover up that he was born in Kenya. (Mr. Obama eventually released the form, which showed that he was born in Hawaii, and Mr. Trump ultimately acknowledged that Mr. Obama really is a native-born American.)
During the 2016 campaign, Mr. Trump often seized on documents as a potential holy grail. At one point, it was sealed pages of a congressional report into the Sept. 11, 2001, terrorist attacks that he argued would show who was behind them. At other moments, he pointed to Mrs. Clinton’s deleted emails or the hacked emails of Mrs. Clinton’s campaign chairman, John D. Podesta, which were released by the website WikiLeaks.
David Strauss, a University of Chicago law professor, said Mr. Trump’s accusations against the F.B.I. and the Justice Department were not mere political rhetoric, but messages with consequences. “We have a president who seems to have no understanding of the professional ethos of the Justice Department, who has no understanding how these people think about their jobs,” he said.
Especially upsetting, some former officials said, is that Mr. Trump has publicly taunted specific individuals — a top F.B.I. official, an F.B.I. lawyer and an F.B.I. supervisor.
“It’s one thing for the president to criticize political appointees — although it is quite odd for him to criticize his own political appointees,” said Alan Rozenshtein, a lawyer who left the Justice Department’s national security division in April and now teaches at the University of Minnesota law school. But to attack career employees at the F.B.I. who are barred by regulations from publicly responding, he said, “that’s really bad.”
Josh Campbell, who spent a decade at the F.B.I. and worked directly for Mr. Comey at one time, wrote in The Times on Saturday that he was resigning so that he could speak out. “These political attacks on the bureau must stop,” he wrote. “If those critics of the agency persuade the public that the F.B.I. cannot be trusted, they will also have succeeded in making our nation less safe.”
One F.B.I. supervisor in a field office said public shaming of his colleagues had wiped out any desire he had to work at the bureau’s headquarters in Washington. “I’d rather chew glass,” he said.
Mary McCord, a former acting assistant attorney general for the national security division, left the Justice Department in May after 23 years. Every new administration, she said, ushered in new priorities and policies. But only Mr. Trump, she said, had put the entire department under a cloud.
“I’ve never seen attacks on the F.B.I. or the D.O.J. like we’ve seen in the last year,” she said. “It makes me just really sad.”
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