A former top staffer for New Jersey Gov. Chris Christie who was recently hired by Donald Trump’s campaign knew about a politically-motivated scheme to cause traffic problems on the George Washington Bridge a month before it was carried out in 2013, the government’s key witness testified on Monday.

David Wildstein, a former Christie appointee at the Port Authority of New York and New Jersey, said on the stand that Bill Stepien, Christie’s former campaign manager, was informed of the plan to close lanes on the bridge less than 24 hours after it was hatched, according to the Associated Press.

Wildstein, who last year struck a plea deal for his role in organizing the so-called Bridgegate scandal, said he also told Stepien that he and other Port Authority staffers would commission a traffic study as a cover-up explanation for the lane closures, the AP reported.

Stepien was not charged in the case. But Christie cut ties with him in January 2014 after emails were released in which Stepien referred to the Democratic mayor of Fort Lee, the target of the Bridgegate plot, as an “idiot.”

At the time, the New Jersey governor asked Stepien to withdraw his name from consideration for chairing the state Republican Party. His consulting contract with the then-Christie-helmed Republican Governors Association also was severed.

The GOP operative languished in political obscurity for several years, until he was hired by the Trump campaign in late August to help coordinate voter turnout.

Christie is serving as the chief of Trump’s transition team, but reportedly had no role in the campaign’s decision to hire Stepien.

Last week, federal prosecutors opened the Bridgegate trial by alleging that Christie knew about the political motivation behind the lane closure plot while it was underway. Assistant U.S. Attorney Vikas Khanna said that Wildstein and another former top Port Authority official, Bill Baroni, “bragged” to Christie about the plan to punish Fort Lee Mayor Mark Sokolich during a 9/11 memorial event in 2013, three days after the closures began.

Baroni and Bridget Anne Kelly, Christie’s former deputy chief of staff, are on trial for conspiracy, fraud, and other charges for their role in planning the lane closures.