When Reince Priebus wants to talk with the most powerful aide in the West Wing, he steps out of his corner office, walks down the hall toward the Oval Office, and knocks on the door of Jared Kushner—sometimes twice. Priebus may be the chief of staff, but it’s he who waits for Kushner, the 36-year-old senior adviser and son-in-law to President Donald Trump, and not the other way around.