While much of the attention in Washington on Monday was on President Obama's controversial pick of former Sen. Chuck Hagel for defense secretary, the president's nominee for CIA director could face his own share of resistance from Congress.
To lead the nation's premier intelligence agency, the president picked White House counterterrorism adviser John Brennan, a 25-year veteran of the CIA and someone Obama described as "one of my closest advisers."
But like Hagel, Brennan has attracted criticism from both sides of the aisle. From the left -- and from some on the right -- he's faced complaints for years that he was too close to controversial CIA programs like the enhanced interrogation techniques that some call torture. That issue led Brennan to withdraw his name from consideration for CIA director back in 2008.
Among Republicans, there is lingering bad blood over his clashes in early 2010 about the administration's handling of would-be Christmas Day bomber Umar Farouk Abdulmutallab. Brennan was accused of playing the role of political attack dog at the time, taking to the media to criticize those lawmakers questioning the decision to read the suspect his Miranda rights shortly after he was captured.
In February 2010, then-Sen. Kit Bond called for Brennan's resignation.
On top of that, Brennan has a history of controversial comments that could re-surface during his Senate confirmation process.
In May 2010, during a speech at the Center for Strategic and International Studies, called jihad a "legitimate tenet of Islam." The technical, broadest definition of jihad is a "struggle" in the name of Islam and the term does not connote "holy war" for all Muslims. Brennan, then, argued it would be "counterproductive" for the United States to use the term, as it would "play into the false perception" that the "murderers" leading war against the West are doing so in the name of a "holy cause."
Before that, during a February 2010 speech in New York, Brennan referred to Jerusalem by its Arabic name, Al-Quds. "In all my travels the city I have come to love most is Al-Quds, Jerusalem, where three great faiths come together," he said.
During the same speech, Brennan also defended a 20 percent recidivism rate among Guantanamo detainees as not "that bad."
In the near-term, Brennan's history with controversial CIA programs could cause the most turbulence for the nominee as he enters the confirmation process.
"The Senate should not move forward with his nomination until all senators can assess the role of the CIA -- and any role by Brennan himself -- in torture, abuse, secret prisons and extraordinary rendition during his past tenure at the CIA, as well as can review the legal authorities for the targeted killing program that he has overseen in his current position," Laura W. Murphy, director of the ACLU's Washington Legislative Office, said in a statement released Monday.
Sen. John McCain, R-Ariz., who is adamantly opposed to waterboarding and other "enhanced" interrogation techniques, also raised concerns about the Brennan nomination.
"I appreciate John Brennan's long record of service to our nation, but I have many questions and concerns about his nomination to be director of the Central Intelligence Agency, especially what role he played in the so-called enhanced interrogation programs while serving at the CIA during the last administration, as well as his public defense of those programs," McCain said, adding that he will consider Brennan's record "very closely."
Brennan has walked a tightrope when it comes to the Bush-era interrogation programs. He has denounced waterboarding as torture. But at the same time, he has defended the overall interrogation program as producing life-saving intelligence.
"There (has) been a lot of information that has come out from these interrogation procedures that the agency has in fact used against the real hardcore terrorists. It has saved lives," he told CBS News in November 2007.
White House officials say the issue is moot at this point because Brennan helped put an end to the "enhanced" techniques. He was on board as Obama's counterterrorism adviser from the very start of his presidency.
Asked Monday about Brennan's role in devising those techniques, White House Press Secretary Jay Carney said: "It is this president who banned torture as one of his first acts in office. And he has implemented that policy and many others with the remarkably capable assistance of John Brennan."
Obama described Brennan as "one of the hardest-working public servants I've ever seen."
Beyond the interrogation program issue, Brennan's defense of the administration in the wake of the Christmas Day bombing attempt could resurface during the confirmation process.
Republicans at the time accused the administration of negligence for reading the suspect his Miranda rights within hours of his arrest, claiming valuable intelligence about Al Qaeda in Yemen was lost for good.
Brennan returned fire in early 2010 with a scathing op-ed in USA Today, writing that "politically motivated criticism and unfounded fear-mongering only serve the goals of al-Qaeda."
Given Brennan's track record over the last four years, a former senior intelligence official questioned whether he could successfully recast himself as neutral -- or whether the appointment would further politicize the CIA's role.
Fox News' Catherine Herridge contributed to this report.