WASHINGTON — The Justice Department’s top leaders listened in stunned silence this month: One of their peers, they were told, had devised a plan with President Donald J. Trump to oust Jeffrey A. Rosen as acting attorney general and wield the department’s power to force Georgia state lawmakers to overturn its presidential election results.

The department officials, convened on a conference call, then asked each other: What will you do if Mr. Rosen is dismissed?

The answer was unanimous. They would resign.

Their informal pact ultimately helped persuade Mr. Trump to keep Mr. Rosen in place, calculating that a furor over mass resignations at the top of the Justice Department would eclipse any attention on his baseless accusations of voter fraud. Mr. Trump’s decision came only after Mr. Rosen and Mr. Clark made their competing cases to him in a bizarre White House meeting that two officials compared with an episode of Mr. Trump’s reality show “The Apprentice,” albeit one that could prompt a constitutional crisis.