His journey provides an unprecedented entry into the corridors of power, and a remarkable lesson in what makes an effective leader. Mr. Comey served as director of the FBI from 2013 to 2017, appointed to the post by President Barack Obama. From prosecuting the Mafia and Martha Stewart to helping change the Bush administration's policies on torture and electronic surveillance, overseeing the Hillary Clinton e-mail investigation as well as ties between the Trump campaign and Russia, Comey has been involved in some of the most consequential cases and policies of recent history.