Trenton, N.J. - A contrite New Jersey Gov. Chris Christie apologized Thursday for a scandal that threatens his political future, announcing that he had fired a senior aide and banished his top campaign adviser for their roles in days of traffic jams orchestrated to punish a small-city Democratic mayor.

Christie at once claimed responsibility as the state's chief executive but also insisted he had no involvement in shutting down a pair of access lanes to the heavily trafficked George Washington Bridge over four days in early September. The Republican governor said he was "blindsided" by this week's release of emails and text messages detailing his office's role in the plot to create severe gridlock in Fort Lee, N.J.

In a meandering, two-hour news conference in his office here at the State Capitol, Christie said he was "embarrassed and humiliated" by an episode that left him feeling "heartbroken" and "betrayed." Despite his reputation for "directness and blunt talk," the governor said, "I am not a bully."

Christie, a leading contender for the Republican presidential nomination in 2016, also tried to tamp down allegations that he had nurtured a culture of intimidation in his administration and his political campaigns.

"This is the exception - it is not the rule - of what's happened over the last four years in this administration," Christie said. He added that he was "stunned by the abject stupidity that was shown here."

Christie repeatedly invoked his ignorance of key events, providing a stark contrast to his carefully cultivated image as a hands-on, can-do chief executive and former prosecutor who helped guide New Jersey in the painful aftermath of Hurricane Sandy.

Christie said he delegates "enormous authority" to his staff, despite his reputation as a micromanager. He said he first learned of the damning emails between his staff and associates by reading The (Bergen, N.J.) Record's breaking news report Wednesday on his iPad at the governor's mansion, as he got ready to shower after his morning workout.

The emails suggest that Christie operatives jammed traffic in Fort Lee to retaliate against Mark Sokolich, the small city's mayor, who did not endorse Christie's 2013 re-election. But Christie claimed he never knew his team was pursuing Sokolich's endorsement and that, until he saw the mayor's picture on television, "I wouldn't have been able to pick him out of a lineup."

Following his marathon news conference, Christie traveled to Fort Lee to apologize personally to Sokolich and the community for the lane closures, which severely delayed commuters, school buses and emergency vehicles.

Although the mayor initially thought a meeting would be disruptive, he later said that he accepted Christie's apology. "I take him for his word," Sokolich said.

The bridge controversy is certain to continue. The office of U.S. Attorney Paul Fishman announced Thursday that it had opened a preliminary inquiry after a referral from the inspector general at the Port Authority of New York and New Jersey, which oversees the bridge. Fishman was nominated as the state's top federal prosecutor in 2009 by President Barack Obama.

In Trenton, former Christie appointee David Wildstein, who is shown helping to orchestrate the gridlock plan in emails, invoked his Fifth Amendment right against self-incrimination in refusing to answer questions in front of the General Assembly's transportation committee. The panel voted unanimously to refer Wildstein to authorities for a possible contempt charge.

'Answers have to be had'

State Senate President Stephen Sweeney, a Democrat who is friendly with Christie, said his party's lawmakers will continue their investigations but will not rush the process. "We don't want to create a political circus," he said, "but answers have to be had."

Thousands of additional pages of emails connected to the legislative inquiry could be made public as early as Friday.

Christie said he could not say "unequivocally" that no other aides were involved in the bridge scheme or other acts of political bullying. But, he said, "if there's any other evidence that comes forward that requires action to be taken, I will take it, no matter how much it hurts me personally or dismays me."

Christie said that he had fired deputy chief of staff Bridget Anne Kelly, who, like other members of his tight-knit inner circle, was considered family. Emails show that Kelly was closely involved in executing the gridlock plan, including a message sent to Wildstein in August declaring, "Time for some traffic problems in Fort Lee."

Christie described Kelly as "stupid" and "deceitful," adding, "I've terminated her employment because she lied to me."

The governor said he told his senior aides before a news conference last month that they had one hour to share any information they may have about the lane closures with Kevin O'Dowd, his chief of staff, and Charlie McKenna, his chief counsel. Kelly said nothing, Christie said, prompting him to unwittingly mislead the public by insisting that the governor's office had nothing to do with the gridlock.

Christie also announced Thursday that he had removed Bill Stepien - his closest political adviser and his campaign manager in 2009 and 2013 - from his political organization, at least temporarily. Christie said he directed Stepien to withdraw his name from becoming state Republican Party chairman and to end his consulting arrangement with the Republican Governors Association, which Christie took over as chairman late last year.

No evidence has surfaced that Stepien was involved in closing the lanes, but emails show he communicated about the incident after the fact with Wildstein, who resigned late last year as the scandal began to escalate.

"I am embarrassed and humiliated by the conduct of some of the people on my team," Christie said. "There's no doubt in my mind that the conduct that they exhibited is completely unacceptable and showed a lack of respect for the appropriate role of government."

Later, the governor added, "I'm a sad guy standing here today."

Christie's calm demeanor and tough words may reassure national GOP operatives and donors for the time being, but lawmakers in Trenton said there would be more subpoenas for Christie's staff.

"It's very hard for me to accept that Bridget Kelly is the key person or that this was her idea," said state Sen. Joseph Vitale, a Democrat. "She may have pushed the button, but we need to know about the other names that have so far been redacted."

The bridge scandal has cast a cloud over Christie's plans to introduce himself to voters around the country in anticipation of an expected presidential campaign. Because of his leadership after Hurricane Sandy ravaged coastal New Jersey in 2012, Christie has been celebrated as a bipartisan straight-talker.

"I am not a focus-group-tested, blow-dried candidate or governor," Christie said Thursday. He added, "I've worked for the last 12 years in public life developing a reputation for honesty and directness and blunt talk, one that I think is well-deserved. But when something like this happens, it's appropriate to question yourself."

When a reporter asked whether he considered resigning, the governor said, "Oh, God no . . . That's a crazy question, man."

Rucker reported from Washington. Washington Post staff writers Bill Branigin and Debbi Wilgoren in Washington contributed to this report.