Mr. McCabe is ensnared in an internal review that includes an examination of his decision in 2016 to allow F.B.I. officials to speak with reporters about an investigation into the Clinton Foundation. The Justice Department’s inspector general concluded that Mr. McCabe was not forthcoming during the review, according to the people briefed on the matter. That yet-to-be-released report triggered an F.B.I. disciplinary process that recommended his termination — leaving Mr. Sessions to either accept or reverse that decision.

Lack of candor is a fireable offense, but like so much at the F.B.I., Mr. McCabe’s fate is also entangled in presidential politics and the special counsel investigation. He was involved from the beginning in the investigation into the Trump campaign’s ties to Russia. He is also a potential witness in the inquiry into whether Mr. Trump tried to obstruct justice.