The lawyer, William J. Olson, was promoting extreme ideas to the president that Mr. Olson later conceded could be regarded as tantamount to declaring “martial law” and could even invite comparisons with Watergate. They included tampering with the Justice Department and firing the acting attorney general, according to the Dec. 28 memo by Mr. Olson, titled “Preserving Constitutional Order,” describing their discussions.

“Our little band of lawyers is working on a memorandum that explains exactly what you can do,” Mr. Olson wrote in his memo, obtained by The New York Times, which he marked “privileged and confidential” and sent to the president. “The media will call this martial law,” he wrote, adding that “that is ‘fake news.’”…

Mr. Olson also encouraged Mr. Trump to fire or reassign Mr. Rosen should he not go along with the plans to use the Justice Department to challenge the election in court, though Mr. Olson acknowledged such action would draw negative news coverage.

“This step will likely bring on a thousand stories making an analogy to ‘Saturday Night Massacre’ in 1973 when President Nixon ordered AG Elliot Richardson to fire Archibald Cox as a special counsel investigating Watergate,” he wrote.

Mr. Olson said a new White House counsel should take steps to ensure a “fair election count” that he conceded would be seen by many as “martial law.”