Robert Mueller became FBI director just days before the attacks of Sept. 11, 2001. Since then, he's been the U.S. government's indispensable man when it comes to national security.
But Mueller's term has expired, and the clock is ticking on an unprecedented extension that Congress gave him two years ago.
The first time the Obama White House thought about a replacement for Mueller, back in 2011, officials threw up their hands and wound up begging him to stay. Congress passed a special law to allow it. Then Republican Sen. Charles Grassley of Iowa put his foot down.
"Extending a director's term was not a fly-by-night decision," Grassley said at a Senate Judiciary Committee hearing. "It also puts the president on notice to begin the process of selecting and nominating a new FBI director earlier than the last attempt."