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."
Behind the scenes, that process is well under way.
The FBI director serves a 10-year term — designed to give that person insulation from partisan politics. But whomever President Obama chooses could become a big part of his legacy.
The administration approached D.C. federal appeals court judge Merrick Garland, who said he didn't want the job, according to two sources familiar with the exchange. Other possible candidates, such as former Chicago U.S. Attorney Patrick Fitzgerald, recently started lucrative jobs in the private sector after spending decades in public service.
That still leaves some serious candidates on the short list, though. One is Lisa Monaco, a career federal prosecutor who once served as Mueller's FBI chief of staff. Monaco developed close partnerships with the intelligence community when she ran the Justice Department's National Security Division, or NSD.
"Our goal in NSD is to serve as practical problem-solvers on operational, legal and policy questions that we confront alongside our partners," Monaco told the American Bar Association earlier this year. "And also, above all, our goal is to keep pace with an evolving threat."
That threat now includes cyberattacks, she added: "The pervasiveness of cybertechnologies and the rate at which they change increases our vulnerability to attack."
Monaco recently moved over to the White House to be Obama's homeland security and counterterrorism adviser. She would be the first woman to become FBI director — no small thing for a president who's trying to diversify his Cabinet.
A second serious candidate is Jim Comey, the former U.S. attorney in Manhattan, where he prosecuted Martha Stewart for lying about stock trades.
Comey, a Republican, went on to become second in command at the Justice Department during the George W. Bush administration. Two years after Comey left the department in 2005, he told the Senate about his threat to resign over a program that's been described as a form of warrantless wiretapping of Americans.
"I couldn't stay if the administration was going to engage in conduct that the Department of Justice had said had no legal basis. I simply couldn't stay," Comey told members of the Senate Judiciary Committee.
During the height of the crisis, Comey worked closely with FBI Director Mueller and sought his help when Bush White House officials showed up at the hospital bed of then-Attorney General John Ashcroft to try to get him to overrule Comey.
"I was very upset. I was angry. I thought I had just witnessed an effort to take advantage of a very sick man who did not have the powers of the attorney general because they had been transferred to me," Comey said.
That episode nine years ago, and Comey's decision to expand the mandate for a special prosecutor investigating the leak of the identity of CIA operative Valerie Plame, did not endear Comey to some Republicans in Congress.
A third name that's come up is David Kris, a longtime Justice Department lawyer who also led the NSD unit before leaving Washington to work in the private sector. Kris literally wrote the book on national security investigations and prosecutions.
But whichever way it goes in the next few weeks, the White House is betting that lawmakers won't play politics with a nomination as crucial as the FBI director.