By choosing Mr. Comey, a Republican, Mr. Obama made a strong statement about bipartisanship at a time when he faces renewed criticism from Republicans in Congress and has had difficulty winning confirmation of some important nominees. At the same time, Mr. Comey's role in one of the most dramatic episodes of the Bush administration — in which he refused to acquiesce to White House aides and reauthorize a warrantless eavesdropping program when he was serving as acting attorney general — should make him an acceptable choice to Democrats.
It is not clear when Mr. Obama will announce the nomination, which was first reported on Wednesday by NPR. Senior F.B.I. officials have feared that if the president did not name a new director by the beginning of June it would be difficult to get Mr. Comey confirmed by the beginning of September, when Mr. Mueller by law must leave his post. The White House declined to make any comment on Mr. Comey.
Mr. Comey, 52, was chosen for the position over the other finalist for the job, Lisa O. Monaco, who has served as the White House's top counterterrorism adviser since January. Some Democrats had feared that if the president nominated Ms. Monaco — who oversaw national security issues at the Justice Department during the attacks in Benghazi, Libya, last September — Republicans would use the confirmation process as a forum for criticism of the administration's handling of the attack.
In the 2004 hospital episode that defined Mr. Comey's time in the Bush administration, the White House counsel, Alberto Gonzales, and Mr. Bush's chief of staff, Andrew H. Card Jr., sought to persuade Attorney General John Ashcroft — who was ill and disoriented — to reauthorize the administration's controversial eavesdropping program.
Mr. Comey, who was serving as the acting attorney general and had been tipped off that Mr. Gonzales and Mr. Card were trying to go around him, rushed to Mr. Ashcroft's hospital room to thwart them. With Mr. Comey in the room, Mr. Ashcroft refused to reauthorize the program. After the episode, Mr. Bush agreed to make changes in the program, and Mr. Comey was widely praised for putting the law over politics.
The Obama administration had initially hoped to announce the nomination several weeks ago, but delayed it after the Boston Marathon bombings.
The bombings have raised questions about Mr. Mueller's legacy and the bureau's counterterrorism efforts. While the F.B.I. has been praised for helping to catch one of the suspected bombers, Dzhokhar Tsarnaev, Congressional Republicans have raised questions about whether the bureau missed a chance to avert the attack. In 2011, it closed a file it had opened on the other suspected bomber, Tamerlan Tsarnaev, who was killed in a shootout with the police that ended with his being run over by a vehicle driven by his escaping brother.
Mr. Comey will inherit a bureau that is far different from the one Mr. Mueller took over a week before the Sept. 11, 2001, attacks. In the aftermath, Mr. Mueller undertook the task of remaking the bureau into an intelligence and counterterrorism agency from one that had concentrated on white-collar crime and drugs. The number of agents has grown to roughly 14,000 from 11,500 under Mr. Mueller, and the bureau has heavily invested in its facilities and capabilities, improving its computer systems, forensics analysis and intelligence sharing.
In the year to come, Mr. Comey, who most recently served as the general counsel for the large Connecticut hedge fund Bridgewater Associates, will be confronted by the bureau's budgetary shortfalls created by across-the-board budget cuts. He will also be forced to expand his knowledge of cybersecurity, which Mr. Mueller made one of the bureau's chief priorities after counterterrorism.
