In 2005, as acting director of the National Counterterrorism Center, Brennan was accused by California Democratic Rep. Henry Waxman and others of withholding terrorism statistics in a State Department report because of an apparent spike in attacks. Brennan said the spike was due to a different, more comprehensive review of attacks, not an increase in terrorism.
However, Brennan has largely stayed out of the spotlight since joining the president's national security team in 2008 as a senior advisor.
The potential for a cleaner Senate nomination also might have brightened his chances, after Obama passed on Susan Rice for secretary of state, and has already faced criticism for nominating Chuck Hagel.
As for who will fill Brennan's shoes as chief counterterrorism advisor to Obama, Cressey believes Morell may step in. That one-for-one exchange is an "obvious switch," he says, particularly after Morell has been working closely with Obama.
"That job requires coordination and implementation. You need somebody from in-house," he says. "[Obama has] a Chuck Hagel from the outside perspective. He's got John Kerry coming in as Secretary as State. You've got two senators with outside perspective. That's plenty."