The former aide, Matt Mowers, spoke to New Jersey lawmakers investigating the traffic jam scandal that's engulfed the governor's administration.
Mowers, 24, is the fifth person subpoenaed to testify before the Democrat-led panel. He worked in Christie's office and on last year's re-election campaign and is now the executive director of New Hampshire's Republican Party.
Mowers said he was not involved in the traffic plot.
"Today, I sit here dumbfounded and disappointed that the actions seemingly taken by a few rogue individuals have tainted the good work that so many have done on behalf of the residents of New Jersey," Mowers said.
The committee is trying to determine who ordered traffic lanes blocked in September at the George Washington Bridge and why. The closures caused gridlock in Fort Lee, the town at the base of the heavily traveled span linking New Jersey and New York, and appear to have been directed at the town's mayor, a Democrat who did not endorse Christie.
Mowers was peppered with questions about his interactions with Fort Lee Mayor Mark Sokolich and about lists of favored towns and public officials maintained by the Office of Intergovernmental Affairs, where Mowers worked before joining Christie's re-election campaign.
Sokolich's name appears on the list.
Mowers' job duties included courting mayors in northern New Jersey for re-election endorsements of Christie.
He acknowledged discussing a possible endorsement with Sokolich early in Christie's campaign. However, he said Sokolich made it clear over drinks in March 2013 that he feared backlash from fellow Democrats and a loss of business contacts if he endorsed the Republican governor. Mowers then sent an email to another government staffer relaying that Sokolich would not be endorsing Christie.
It's regrettable, he wrote to a colleague, "because I really liked the guy."
The Christie campaign aggressively sought endorsements from Democrats because a big re-election win in a Democrat-leaning state was thought to improve his standing in a crowded 2016 Republican presidential field. Though he easily won re-election, the scandal has raised questions about Christie's viability as a presidential candidate.
Christie has repeatedly denied any knowledge of the planning or execution of the lane closings. Federal prosecutors are investigating the closings and separate allegations that the administration threatened to withhold Superstorm Sandy recovery aide to a city unless its mayor agreed to support a favored redevelopment project.
Mowers testified that mayors were not shunned for not supporting Christie. But previously released emails showed certain mayors became identified as "hands off" within the Office of Intergovernmental Affairs, and proactive communication to them ceased. Sokolich's messages complaining about gridlock in his town were ignored.
The emails also show regular communication between Christie's government staff and his political team, leading Sen. Loretta Weinberg to conclude that "the lines were blurred" between government and politics.
Former aide Bridget Kelly called Mowers on Aug. 12 to confirm that Sokolich would not be endorsing the governor. The next morning, Kelly set the lane closings in motion with an email, "time for some traffic problems in Fort Lee."
Christie, who says he is still considering running for president and will decide his political future later, recently said the lane closings would be "a footnote" by 2016. But his prediction came the same day his former campaign manager contradicted Christie's timeline of the bridge scandal.
Political operative Bill Stepien said Christie misspoke Dec. 13 when he told reporters he had received assurances that no one close to him knew about the lane closings. Stepien said he informed Christie on Dec. 12 that he knew about the plan to divert traffic but was told it was part of a study. Patrick Foye, the executive director of the bridge agency, who ordered the lanes reopened after four days, said he was unaware of any traffic study.
Stepien said the idea was brought up by David Wildstein, an administrative operative at the bridge agency, who frequently came to Stepien with "crazy ideas."
Wildstein was forced to resign, and Kelly was fired. Christie also cut ties with Stepien, a valued political strategist who had been in line to run any national Christie campaign, saying he no longer trusted his judgment.