The White House chief-of-staff role is the hardest gig in Washington, D.C. Dick Cheney blamed the job for giving him his first heart attack, during the Ford Administration. A hapless chief of staff can break a Presidency; an effective one was nicknamed the Velvet Hammer. In January, Joe Biden’s first chief of staff, Ron Klain, was replaced by Jeffrey Zients. In a conversation from last winter, the staff writers Susan B. Glasser, Jane Mayer, and Evan Osnos use Klain’s departure as a jumping-off point to discuss what it’s actually like to run a White House.