A former political ally of New Jersey Gov. Chris Christie pleaded guilty in federal court Friday over his role in creating traffic jams near the George Washington Bridge in 2013, as two other ex-officials were also indicted in the high-profile case. 

The guilty plea by David Wildstein, former Port Authority of New York and New Jersey official, marks the first conviction in an investigation that has caused political headaches for Christie, a Republican governor and potential presidential candidate. Wildstein admitted to causing significant traffic problems in Fort Lee in September 2013 in retaliation against the city's mayor, who did not endorse Christie's re-election bid. 

An indictment was unsealed shortly afterward against Bridget Kelly, who was Christie's deputy chief of staff, and Bill Baroni, who was Christie's top appointee at the Port Authority. 

"The indictment alleges, and Wildstein admitted, that the three defendants used Port Authority resources to exact political retribution against a public official who would not endorse the Governor for re-election, and concocted and promoted a bogus cover story to execute their plan and to cover their tracks," U.S. Attorney Paul Fishman said in a statement. 

Fishman said they deliberately waited until the first day of school in September 2013 to further hurt Fort Lee residents. Kelly and Baroni are charged with nine counts, including conspiracy and fraud. 

Wildstein has said he came up with the plans along with Kelly and Baroni. He said they also agreed to cover it up by claiming the lane closings were part of a traffic study. 

Friday afternoon, Kelly appeared at a news conference and denied any guilt."For over a year, I have remained quiet while many of the people I believed in, trusted and respected have attempted to publicly discredit and even humiliate me," she said. "I am here to say that I will no longer allow the lies that have been said about me or my role in the George Washington Bridge issue go unchallenged."

Wildstein, however, did not implicate Christie in the scheme that has cast a long shadow over the Republican governor's White House prospects in 2016. The outspoken governor is still weighing a bid, and has held back as several other Republicans have announced their 2016 campaigns. 

In an exclusive pre-taped interview with Fox News' Bret Baier broadcast Friday, Christie said, "there has not been one fact, Bret, that has come out in the course of the last 15 months that has contradicted anything I have said after an internal investigation, after a highly partisan Democratic legislative investigation or after a U.S. attorney investigation."

A separate investigation ordered by Christie and conducted by a law firm with ties to him determined that he played no role in the 2013 bridge affair.

The federal investigation was launched after two of the three access lanes to the bridge in Fort Lee were shut down for four mornings in September 2013, causing massive delays.

The simmering scandal erupted a year ago, with the disclosure of an email from Kelly to Wildstein. It read, "Time for some traffic problems in Fort Lee." Wildstein's reply was, "Got it."

By the time that email was made public, Wildstein had already resigned, as had Baroni. The governor fired Kelly and cut ties with Bill Stepien, his two-time campaign manager, amid the scandal. 

Christie, the former chairman of the Republican Governors Association and an active GOP fund-raiser, has not announced that he will run for the 2016 Republican presidential nomination, but has been widely viewed as a potential candidate. Christie has launched a political action committee that allows him to pay for travel and a staff, for a presidential run.

The Associated Press contributed to this report.