(CNN) -- Dennis Blair, the president's top intelligence adviser, announced his resignation after 16 months of power struggles, politics and personality clashes.





Blair was the third person to serve as director of national intelligence since the position was created five years ago. His resignation is effective May 28.





Although President Obama praised Blair for his "remarkable record of service," there has been tension between the two. Blair found himself at odds with the White House over the scope of his role, and there was indirect conflict with others in the intelligence community.





"From the beginning the White House did not have the same view of what the DNI should be," according to a source familiar with the situation.





"[Blair] is a manager and a leader. He is not a politico. He doesn't run around doing political stuff," the source said, acknowledging the Blair's candor got him in trouble.





Blair, a retired four-star Navy admiral, has served in the post since January 2009. His office oversees 17 federal intelligence agencies, including the CIA, FBI and Department of Homeland Security.





Word of his resignation came two days after the Senate Intelligence Committee released a report that sharply criticized the National Counterterrorism Center, overseen by Blair's office, for failing to coordinate properly intelligence activities to detect the attempted Christmas Day airline bombing.





The report highlighted 14 points of failure and said that the center was not organized to fulfill its mission.





Blair, who also caught some of the blame for the more recent failed Times Square bombing attempt, responded to the report by noting changes made in response to the Christmas incident, including creation of a National Counterterrorism Center analytical unit dedicated to following up on terrorist threat information. However, Blair's statement noted that "institutional and technological barriers remain that prevent seamless sharing of information."





Although Blair's resignation was not a complete surprise for those in the intelligence community, he was not expected to step down for another month, senior intelligence officials said.





He decided to leave sooner than expected when Obama asked CIA Director Leon Panetta and national security adviser James Jones to go to Pakistan and Blair was not asked to participate, the sources said.





"When the president looked to Leon Panetta and Jim Jones to go to Pakistan on this very serious threat, it was a slap at him. It was an indication of a lack of confidence in Adm. Blair," said Fran Townsend, CNN national security contributor who was President George W. Bush's chief anti-terrorism and homeland security adviser.





One Senate source said Blair has been unhappy and frustrated. "He was losing every turf battle to Panetta," the source said.





Blair and Obama also didn't have a good connection, Townsend said.





"You've got a very bright, engaged president and with a lot of charisma, and there wasn't a real chemistry between them," she said.





The DNI was intended to be the CEO of the intelligence community, looking at the 17 agencies' budgets, capabilities, training and cross-department communication.





When the position was created, the DNI was given a lot of responsibility but not enough authority, Townsend said.





"It's clear in this case between Adm. Blair and President Obama there was a mismatch and misunderstanding of expectations and responsibilities. And it will be very important that whoever the new DNI is, understands and accepts what the president's view of that position is," she said.





Even before Blair officially turned in his resignation, the White House already had spoken to potential replacements, the senior intelligence officials said.





John Hamre, a defense official in the Clinton administration; retired Air Force Lt. Gen. Jim Clapper, defense undersecretary for intelligence; and former Sen. Chuck Hagel, R-Nebraska, are considered top contenders.





CNN's Kristi Keck, Gloria Borger and Jeanne Meserve contributed to this report.
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