NEWARK -- In opening arguments in the criminal trial of the George Washington Bridge lane closure scandal, federal prosecutors said Monday morning that David Wildstein would testify that he told Gov. Chris Christie about the scheme to close lanes at the bridge at the very moment traffic was at a standstill in Fort Lee.

Assistant U.S. Attorney Vikas Khanna said Wildstein will testify that he and defendant Bill Baroni made Christie aware of the plan while they were attending Sept. 11 commemorations in Manhattan.

"The evidence will show that ... they bragged about the fact that there were traffic problems in Fort Lee and that Mayor Sokolich was not getting his calls returned," Khanna said.

Wildstein's attorney once suggested "evidence exists" Christie knew about the traffic jams. The former Port Authority executive, who was second in command at the bi-state agency, pleaded guilty last year.

Since then, photographs emerged showing Christie talking to Wildstein and Baroni during a Sept. 11 memorial ceremony.

Khanna also told jurors Wildstein, who pleaded guilty to federal crimes and turned cooperating witness for prosecutors, would take the stand in the trial and "admit that he was the one who came up with that idea."

"He will also tell you that (Bridget Anne) Kelly instructed him to take that action and Baroni blessed it," he said.

On trial are Kelly, the governor's former deputy chief of staff, and Baroni, once a close associate and deputy executive director of the Port Authority of New York and New Jersey, which operates the bridge. They are charged with nine counts of conspiracy, fraud and related charges in connection with the September 2013 toll lane shutdowns at the bridge -- an incident that caused massive traffic problems in Fort Lee in what prosecutors called an act of political retribution targeting Mayor Mark Sokolich for his refusal to endorse Christie for re-election.

Calling the plan as "mean spirited and vindictive," Khanna said Christie's former allies not only caused a "crushing traffic jam" in the city of Fort Lee, but broke federal laws.

Khanna described for jurors the alleged vengeful scheme put in motion by Kelly and Baroni.

"Punishing the mayor was exactly what was on Bridget Kelly's mind," Khanna said, at the beginning of the trial that could put Baroni and Kelly behind bars for up to 20 years.

Khanna argued the two "worked hand in hand" to put pressure on a local elected official they hoped would endorse Christie's re-election bid. The pair -- along with Wildstein -- had their sights set on Fort Lee Mayor Mark Sokolich.

Sokolich was a coveted endorsement for Christie's re-election, but he later caught the ire of Kelly and Wildstein after it became clear the Democratic mayor wouldn't back the incumbent Republican governor.

"In 2013, Wildstein took political directions from Gov. Chris Christie's office ... and in doing so, he took directions from Bridget Kelly," Khanna said.

"Wildstein had told her those lanes could be used as leverage against Mayor Sokolich," he said. "Punishing people by using traffic was exactly what was on Kelly's mind at this time."

Khanna described the chaos of the traffic jam that wreaked havoc on Fort Lee for four days in September 2013, painting Kelly and Baroni as public officials who put their ambitions over their primary duties as stewards of the public.

"The defendants abused their powers," Khanna said. "The chose personal and political revenge over the safety of the people of Fort Lee."

Ted Sherman may be reached at tsherman@njadvancemedia.com. Matt Arco may be reached at marco@njadvancemedia.com. Follow him on Twitter @MatthewArco or on Facebook. Follow NJ.com Politics on Facebook.