Republican Gov. Chris Christie's office used the bistate agency that runs the New York area's bridges, tunnels, ports and airports as a clearinghouse for political favors aimed at gaining endorsements from local Democratic politicians, a witness testified Friday in the fraud trial of two former Christie allies.

Among those directly involved in the effort or aware of it were Bridget Kelly and Bill Baroni, who are accused of creating traffic gridlock at the George Washington Bridge in 2013 to punish one of those mayors for not endorsing Christie, according to David Wildstein's testimony.

Wildstein said Christie and his former campaign manager, Bill Stepien, were among those who discussed the strategy at a meeting about Christie's 2013 re-election.

Stepien and another former Christie aide who testified Friday now work for Republican presidential nominee Donald Trump's campaign.

Wildstein has pleaded guilty in the scheme to tie up traffic at the bridge, which spans the Hudson River and connects Fort Lee with New York City.

Baroni was Wildstein's boss at the Port Authority of New York and New Jersey, the agency that operates the bridges, airports and other facilities including the World Trade Center. Kelly was Christie's deputy chief of staff and headed an office responsible for outreach to county and municipal officials.

They are accused of reducing access lanes to the bridge and face fraud, conspiracy and civil rights charges. They have pleaded not guilty and have said the government has twisted federal law to turn their actions into crimes. They also have said other people with more power and influence were involved in the lane closures but aren't being prosecuted.

Christie has denied knowing about the bridge scheme until well after it was carried out, and a taxpayer-funded report he commissioned absolved him of wrongdoing. He hasn't been charged.

Christie's office and a Port Authority spokesman didn't return messages seeking comment Friday. Stepien's lawyer declined to comment.

The favors doled out to towns and local officials included grants, emergency response equipment, private tours of the World Trade Center redevelopment site and pieces of steel salvaged from the destroyed twin towers, Wildstein said. A former Christie campaign staffer testified Kelly's office kept a spreadsheet noting what favors mayors had received and, on a scale from 1 to 10, their likelihood of endorsing Christie.

While the Port Authority would provide the benefits, Wildstein testified, the governor's office would control the process and take most of the credit in its quest to curry favor with politicians from whom it sought endorsements.

"That was the system that had been established," he said. "All use of Port Authority resources had to be approved by the governor's office. And the governor's office always was the deliverer of good news."

During testimony earlier Friday, former Christie campaign staffer Matt Mowers said Christie wrote a letter to the Port Authority supporting the purchase of commuter shuttle buses Democratic Fort Lee Mayor Mark Sokolich had requested. Sokolich eventually declined to endorse Christie in 2013 and was the target of the lane-closing scheme, prosecutors say.

Mowers, who now works for Trump, also testified he told Kelly about Sokolich's decision on Aug. 12, 2013, the day before Kelly sent an email to Wildstein saying, "Time for some traffic problems in Fort Lee."

Kelly has said her emails were meant to be sarcastic.

Wildstein, at the beginning of his testimony, said he and Baroni often talked of the "one-constituent rule," referring to Christie as the only constituent they needed to serve.

Wildstein and Christie attended high school together, and Wildstein was hired by the Port Authority to a position created for him.

Port Authority Executive Director Patrick Foye testified Wildstein was universally hated at the agency but was "protected" by Christie, but Christie has denied the two had a close relationship.

During opening statements, prosecutors said Wildstein will testify he bragged to Christie about the lane closures on the third day of the four-day shutdown. Christie's office has pointed to a statement he gave in 2014, denying he knew about the plot while it was ongoing.