NEWARK - As the criminal trial of two former aides to Gov. Christie enters its sixth week, the federal government faces one of its biggest challenges yet: cross-examining Bridget Anne Kelly, a single mother of four who they allege conspired to punish a local mayor by causing a week of traffic jams near the George Washington Bridge.

That job falls to Vikas Khanna, 36, an assistant U.S. attorney who grew up in Holland, Bucks County. Khanna now lives in Hoboken with his wife, Lauren, and their 3-year-old daughter, but still keeps close tabs on the Eagles and Phillies.

Khanna, who went to Council Rock High School before graduating from Princeton and Harvard Law, is also expected to deliver the government's rebuttal after defense attorneys make their closing arguments.

That means he'll have the final word before jurors decide whether Kelly and Bill Baroni, Christie's former top executive appointee at the Port Authority of New York and New Jersey, are guilty beyond a reasonable doubt of misusing Port Authority resources to retaliate against Fort Lee Mayor Mark Sokolich for his refusal to endorse Christie's reelection campaign in 2013.

Kelly is a "sympathetic figure," in part because she "has so much at stake" with children still at home, said Joseph A. Hayden Jr., a veteran criminal defense attorney and former state deputy attorney general.

"The challenge for the prosecution will be to be rigorous but fair, and at all times avoid being snide," Hayden said.

Kelly, 44, told jurors Friday that for years she worked five minutes from her Ramsey, Bergen County, house, and could bring her children to the office. With a divorce pending and her kids in parochial school, she took a higher-paying position in Trenton to work for Christie, an hour and 45 minute commute each way.

Soon, Kelly came to fear the Republican governor.

An angry Christie once threw a water bottle at her in Seaside Heights in the aftermath of a boardwalk fire, she testified.

"Big tough guy, huh?" said Kelly's attorney, Michael Critchley Sr.

Khanna opened the trial Sept. 19 with the bombshell that Baroni and David Wildstein, a former Port Authority official and the government's key witness, had "bragged" to Christie at a Sept. 11 memorial service about the fact that "there were traffic problems in Fort Lee and that Mayor Sokolich was not getting his calls returned."

Christie has said he doesn't recall the conversation and has denied having contemporaneous knowledge of the lane closures.

In his six years at the U.S. Attorney's Office, Khanna has prosecuted cases ranging from drug conspiracies to extortion, including that of a Jersey City fire inspector who pleaded guilty to facilitating prostitution with certificates of occupancy in exchange for bribes.

He was also part of the team that prosecuted David Samson, a Christie confidant who pleaded guilty in July to abusing his power as chairman of the Port Authority to shake down United Airlines executives for a bribe.

The office of U.S. Attorney Paul Fishman declined to make Khanna available for an interview, and Fishman declined to comment. His office provided biographical information.

"Knowing Vikas, I know he will be incredibly prepared, take a very sort of rational and reasoned approach to this," said Scott Resnik, a former federal prosecutor who recruited Khanna in 2007 to his new white-collar criminal defense practice in the New York office of Katten Muchin Rosenman LLP.

"He's very measured and level-headed. I would expect his cross-examination to be very well thought out, very well organized, and very coolly delivered," Resnik said.

During the bridge trial, Khanna has delivered some of his more colorful remarks in private conversation with defense attorneys and U.S. District Judge Susan D. Wigenton.

Two days after the Oct. 9 presidential debate, he chastised Baroni's attorney, Michael Baldassare for a "Trumpian interruption," according to a court transcript.

"Come on," Baldassare said. "Now that's a low blow, Vikas. That's bad."

On the first day of trial, jurors heard Critchley, Kelly's attorney, assert that Christie and his inner circle were "coteries of cowards" who would do anything to advance his political ambitions - including throwing Kelly, deputy chief of staff for intergovernmental affairs, "under the presidential bus."

On the stand Friday, Kelly, speaking publicly about the case for the first time since she was indicted in May 2015, recounted interactions with Christie that brought her to tears.

After a boardwalk fire destroyed small businesses in Seaside Heights in September, Christie instructed Kelly to convene a roundtable of the business owners and cabinet officials, she said. When Kelly advised him to introduce and welcome everybody before passing the discussion off to others, he replied, "What do you think I am, a f-ing game show host?"

That's when Christie threw his water bottle at her. "I moved out of the way, but it hit my arm," she told jurors, crying.

Kelly testified that she believed the lane closures were part of a Port Authority traffic study and that she had no idea Wildstein wanted to cause traffic problems to punish Sokolich.

Kelly will continue her direct testimony on Monday.

Prosecutors were aggressive with Kelly's codefendant, Baroni, a former state assemblyman and senator who had appeared before congressional and legislative hearings.

Assistant U.S. Attorney Lee Cortes was combative during cross-examination, asking questions in a rapid-fire manner, as if he was trying to goad Baroni into performing as the animated Christie operative who appeared at a 2012 congressional hearing. Christie had dispatched Baroni, then at the Port Authority, to rough up U.S. Sen. Frank Lautenberg over his opposition to toll hikes.

At one point, Cortes suggested Baroni was being too expansive in his answers, instead of saying yes or no.

"Mr. Baroni, if I want an explanation, I'll ask. OK?" Cortes said sharply, prompting an objection from Baroni's attorney. "You understand?"

"I'm sorry," Baroni replied.

Khanna is unlikely to make such an interjection with Kelly. But he's no pushover.

When defense attorneys complained to the judge during a sidebar conversation that prosecutors had consistently failed to correct false statements by their witnesses, Khanna dismissed the idea as "ridiculous."

"This is quite frankly insulting to be continually attacked on ethical issues whenever there's a disagreement about evidence," Khanna told the judge, according to a transcript of the conversation. "And I would just ask that the record reflect that. The Government has acted appropriately and has not committed any ethical violations here.

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@AndrewSeidman