NEW YORK — Chris Christie got high marks for deftly managing his George Washington Bridge crisis – until he channeled Richard Nixon.

The New Jersey governor was apologetic and remorseful during a news conference in Trenton on Thursday after sacking the aide he said was behind a scheme to shut down access lanes and snarl traffic in a political rival’s town. Then he answered a question about whether the bridge maneuver backed up critics’ contention that he’s a bully by saying, “I am not a bully.”

With those words the Republican broke a basic tenet of damage control by echoing one of his foes’ favorite attack lines, said Davia Temin, head of the Temin & Co. crisis management firm in New York. “The No. 1 rule is don’t repeat the allegations. I am not a bully or I am not a crook – it’s the wrong thing to do.”

Christie did most everything else right, crisis managers said, taking responsibility, expressing outrage, promising soul-searching, apologizing to the rival, firing the aide and insisting he knew nothing about what, inescapably, is being called Bridgegate.

All of that reinforced his branding as a strong straight-talker who could be in the White House, said Mark Irion, president of Levick, a Washington-based strategic communications firm. He said the risk is that voters will also be reminded the 51-year-old has a reputation as a gruff guy who holds grudges.

“His real political Achilles’ heel is that he may be a small-minded political bully, and not that straightforward consensus builder that he wants to be known as nationally,” Irion said. “His ultimate weathering of this is going to be determined by his ability to give absolutely no occasion for his opponents to reinforce that negative belief about him.”

Crisis management experts praised the governor for taking pages straight from their manual once incriminating emails and texts emerged to show that aides and political associates had orchestrated the closure of the lanes for four days in September. The resulting jam paralyzed Fort Lee, a town at the end of the bridge connecting New Jersey to Manhattan and whose mayor, Mark Sokolich, refused to endorse Christie for governor in the election in November. The intention was to punish the mayor, according to the messages.

Before they were made public, Christie had laughed off the incident, which delayed commuters and crews on their way to medical emergencies. At one point he responded to questions about the gridlock by saying he’d put traffic cones down himself. He said Thursday that he would never have joked about it if he’d known what people close to him had done.

“There’s no justification for that behavior,” he said, saying he’d been “stunned,” and was “heartbroken.”

Christie made a pilgrimage to Fort Lee after the news conference, to meet with residents and deliver an apology to Sokolich. Unlike dozens of other Democrats, Sokolich didn’t back Christie against his Democratic challenger.

Even as the governor’s visit was publicized, the “bully” quote was flashing on television screens and lighting up Twitter with comparisons to other infamous one-liners. Among them: Delaware Republican Senate candidate Christine O’Donnell saying “I am not a witch” in response to chatter about a decades-old comment that she’d dabbled in witchcraft, and President Bill Clinton declaring about Monica Lewinksy, “I did not have sexual relations with that woman.”

What Christie said is now “a soundbite that will repeat again and again for years to come,” said Rob Baskin, a president and general manager for the public-relations firm Weber Shandwick in Atlanta, in an email.

The lasting impact of an unfortunate comment is hard to gauge. O’Donnell lost her 2010 race. While Clinton was impeached over his affair with Lewinksy, he wasn’t convicted and remained in office. Nixon uttered “I am not a crook” months before he resigned the presidency over Watergate.

Christie also used a phrase – “mistakes were made” – that’s been ridiculed by linguists and political analysts as a classic passive-voice avoidance idiom. Starting with President Ulysses S. Grant in 1875, those who’ve been quoted as using it while talking about scandals or controversial decisions include President Ronald Reagan and Secretary of State Henry Kissinger.

Christie explained at the press conference why he isn’t a bully but may be viewed as one: “I don’t hide my emotions from people. I am not a focus-group tested, blow-dried candidate or governor. Now, that has always made some people, as you know, uneasy. Some people like that style, some people don’t.”

As governor, he’s dressed down opponents and yelled at people on the street. Irion, the communications strategist, said Christie’s handling of the bridge affair could drown out those images. He said swiftly sending the aide packing was a good start.

Christie said he fired Bridget Anne Kelly, a deputy chief of staff, after learning on Jan. 8 that she’d lied when asked a month ago whether she knew about the lane closings that turned the typical 30-minute drive across the bridge into a trip of four hours or more. The emails showed that Kelly on Aug. 13 told David Wildstein, a Christie appointee at the Port Authority of New York and New Jersey, which operates the bridge, that it was “time for some traffic problems.”

A New Jersey judge Thursday refused to block a subpoena by the Democratic-controlled state Assembly for Wildstein to testify in Trenton. At the committee hearing, Wildstein invoked his right to remain silent so as not to incriminate himself.

The panel ruled Wildstein in contempt. Its chairman, Assemblyman John Wisniewski, said the committee will subpoena more documents and seek to compel more testimony. Kelly will be among the next round of subpoenas, he said.

With federal prosecutors also investigating, Bridgegate will live on. Irion said Christie and his team will have to stay focused and be sure he doesn’t lose the feistiness that’s helped make him so popular.

“His brand is not to be a careful, calculating politician,” Irion said. “He can’t afford to pull up – and be so careful that he ceases to be Chris Christie.”