The highest-ranking official in New Jersey Gov. Chris Christie’s administration to testify before lawmakers about the traffic jam plot that has ensnared the administration told them Monday that he believed a subordinate who said she had nothing to do with the scheme, a claim that was later revealed to be false.

The official, Chief of Staff Kevin O’Dowd, also told the panel that he played no role in the political retribution plot, in which lanes leading to the George Washington Bridge to New York City were closed for days in September, creating massive backups in the town of Fort Lee.

“I had no prior knowledge of, or played no role in, the decision to close the lanes at the George Washington Bridge,” O’Dowd said in his opening statement.

The subordinate, Bridget Kelly, was fired after emails showed she set the plot in motion by writing, “Time for some traffic problems in Fort Lee.”

The scandal has threatened the presidential ambitions of Christie, considered a top contender if he decides to run in 2016. He has denied advance knowledge of the scheme. The U.S. attorney’s office is also investigating the lane closings.

O’Dowd was Christie’s pick to be the state’s attorney general, but the nomination stalled because of the scandal. At an appearance Monday in Camden, outside Philadelphia, Christie said he retains confidence in his top aide and said he would re-nominate him if O’Dowd still wants the position. Both men are former federal prosecutors.

O’Dowd said that on Dec. 12, months after the lane closings, Christie instructed him to ask Kelly whether she was involved. O’Dowd said he “trusted and believed” Kelly when she assured him she had nothing to do with the plot.

The next day at a news conference, Christie denied that anyone on his staff or re-election campaign had a role in the scheme.

O’Dowd, who supervised Kelly, said he doesn’t think he could have done anything to prevent the lane closings.

Another person who lost his job amid the scandal, former Christie campaign manager Bill Stepien, was in the audience along with his lawyer for O’Dowd’s testimony.

They left at a break without commenting.

(AP)