Jane Mayer of The New Yorker is a careful investigative reporter. Her most recent book is “Dark Money,” which explores the billionaires’ assault on democracy.

She wrote a post about James Comey and his decision to go rogue, breaking well-established policies at the Justice Department, not to make unsubstantiated accusations and not to meddle in elections.

She writes:

“Comey’s decision is a striking break with the policies of the Department of Justice, according to current and former federal legal officials. Comey, who is a Republican appointee of President Obama, has a reputation for integrity and independence, but his latest action is stirring an extraordinary level of concern among legal authorities, who see it as potentially affecting the outcome of the Presidential and congressional elections.

“You don’t do this,” one former senior Justice Department official exclaimed. “It’s aberrational. It violates decades of practice.” The reason, according to the former official, who asked not to be identified because of ongoing cases involving the department, “is because it impugns the integrity and reputation of the candidate, even though there’s no finding by a court, or in this instance even an indictment.”

“Traditionally, the Justice Department has advised prosecutors and law enforcement to avoid any appearance of meddling in the outcome of elections, even if it means holding off on pressing cases. One former senior official recalled that Janet Reno, the Attorney General under Bill Clinton, “completely shut down” the prosecution of a politically sensitive criminal target prior to an election. “She was adamant—anything that could influence the election had to go dark,” the former official said.

“Four years ago, then Attorney General Eric Holder formalized this practice in a memo to all Justice Department employees. The memo warned that, when handling political cases, officials “must be particularly sensitive to safeguarding the Department’s reputation for fairness, neutrality, and nonpartisanship.” To guard against unfair conduct, Holder wrote, employees facing questions about “the timing of charges or overt investigative steps near the time of a primary or general election” should consult with the Public Integrity Section of the Criminal Division.

“The F.B.I. director is an employee of the Justice Department, and is covered by its policies. But when asked whether Comey had followed these guidelines and consulted with the Public Integrity Section, or with any other department officials, Kevin Lewis, a deputy director of public affairs for the Justice Department, said, “We have no comment on the matter.”