NEWARK, N.J. - The architect of an alleged political-payback scheme to cause massive traffic jams near the George Washington Bridge in September 2013 testified Friday that he and another top New Jersey appointee at the bistate Port Authority served just "one constituent": Gov. Christie.

"If it was good for Gov. Christie, it was good for us; if it was not good for Gov. Christie, it was not good for us," David Wildstein said.

Chief among the Republican governor's priorities was using the Port Authority of New York and New Jersey to help win endorsements for his reelection campaign three years ago, Wildstein testified.

On behalf of the governor, Wildstein said, he and Bill Baroni, Christie's top executive appointee at the independent agency, tapped it to provide towns with grants, offer elected officials tours of the World Trade Center site, and distribute 100 flags that flew over ground zero on the 10th anniversary of the Sept. 11, 2001, terrorist attacks.

In a May 2011 email to Bridget Anne Kelly, then Christie's deputy chief of staff, who along with Baroni is on trial in the bridge case, Wildstein referred to the Port Authority as a "goody bag."

"I like goody bags," she replied, according to evidence admitted in court. "I appreciate it."

Taking the stand for the first time in the trial that began Monday, Wildstein said Baroni also observed the same "one-constituent" rule.

"The only person who mattered was Gov. Christie. He was the one constituent," Wildstein, who has pleaded guilty and is the government's star witness, told the court.

Asked by Assistant U.S. Attorney Lee Cortes how he knew he was abiding by the rule, Wildstein said, "I knew because we were either told it by the one constituent - Gov. Christie - or by members of Gov. Christie's staff. We received specific instructions."

Wildstein said he came up with the phrase and discussed it with Baroni at a Starbucks store in New York City after Baroni accepted his job as deputy executive director at the Port Authority in 2010.

Baroni wanted to hire Wildstein as his No. 2 to be the "bad cop" who would work "aggressively" to advance New Jersey's interests at the agency.

"My job was to advance Gov. Christie's agenda," Wildstein testified.

Friday marked Wildstein's first public appearance since he appeared in federal court here in May 2015 to plead guilty to conspiracy charges.

Bearded and diminutive, Wildstein, 55, who wore a dark suit, looked directly at jurors as he spoke. He sometimes betrayed a grin as he explained his background, such as when he described his use of the pseudonym "Wally Edge" to disguise his identity as the founder of an influential political blog.

Wildstein said he ran the blog from 2000 to 2010, after which he joined the Port Authority.

The name was a riff on Walter Edge, a former New Jersey governor. Wildstein said he had befriended a member of the Edge family.

Wildstein is to resume his testimony Monday, and defense attorneys are expected to cross-examine him for several days.

Prosecutors say Baroni and Kelly conspired with Wildstein and "others" in 2013 to cause gridlock in Fort Lee, Bergen County, to punish the town's Democratic mayor for refusing to endorse Christie's reelection campaign.

Then they covered it up with a sham story that the lane closures were part of a traffic study, according to prosecutors. Baroni and Kelly are charged with misusing Port Authority resources, wire fraud, civil rights violations, and related conspiracy counts.

Defense attorneys say Wildstein tricked their clients into thinking the study was legitimate and is lying about it to try to avoid prison.

Wildstein said that after some initial hesitation - he didn't think working in government was a "good fit" - he ultimately signed on to be director of interstate capital projects, which paid an annual salary of $150,000.

He said in effect he served as Baroni's chief of staff.

Just before Baroni, a former Republican state senator, was to begin his new job at the Port Authority in 2010, Wildstein said, he explained to his friend that "he was no longer an elected official; he was no longer running for public office; he no longer had a large constituency."

Wildstein said he told Baroni that "his best means of succeeding in his new job at the Port Authority would be to view Chris Christie as his only constituent. The only person he needed to make happy was Gov. Christie."

To demonstrate the point, prosecutors showed jurors an email Wildstein sent to Baroni that linked to a news article in which a GOP assemblyman had criticized the Port Authority-operated Newark Liberty International Airport.

"Schmuck of the week," Wildstein wrote in the subject line.

"Why the hell didn't he just call?" Baroni replied. Assemblyman Jon Bramnick, Wildstein explained in court Friday, didn't follow the "one-constituent" rule.

Wildstein said he and Baroni started using the Port Authority as a tool for Christie's 2013 campaign in May 2010 - the month Wildstein joined the agency and four months into the governor's first term.

Christie, Kelly, and Bill Stepien, a former Christie aide who ran both of his gubernatorial campaigns, instructed Wildstein to use the agency for the purpose of winning endorsements, Wildstein said.

Christie's office didn't respond to a request for comment, and Stepien's attorney declined to comment on Wildstein's testimony.

"All use of Port Authority resources had to be approved by the governor's office," he said at another point during his two hours of testimony. To that end, Wildstein said, he frequently sought Kelly's and Stepien's input.

Prosecutors showed jurors emails exchanged between Kelly and Wildstein that suggested he didn't allow the Port Authority to approve such requests as the donation of a vehicle without Kelly's consent.

In August 2011, Baroni asked Wildstein how he should handle a request for a World Trade Center tour, according to emails introduced in court.

"Through Bridget, like everything else," Wildstein replied.

Asked by Cortes if Kelly generally provided Wildstein with direction, he said yes.

"I viewed Ms. Kelly as my boss," he said.

Across the courtroom, Kelly shook her head, and her lawyers leaned back in their chairs, smirking.

The emails could be important to prosecutors. They say Kelly instructed Wildstein to close lanes near the bridge, and that he followed her orders.

"Time for some traffic problems in Fort Lee," she wrote in August 2013 after confirming the town's mayor would not be endorsing Christie, according to prosecutors.

"Got it," Wildstein replied. A month later, he ordered the lanes closed.

Patrick Foye, the agency's executive director and an appointee of New York Gov. Cuomo, would order them reopened four days later.

aseidman@phillynews.com

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@AndrewSeidman