NEWARK, N.J. — Two former close allies of New Jersey Gov. Chris Christie were charged with conspiracy Friday after a third key figure admitted plotting with them to snarl traffic leading to the busy George Washington Bridge for four days in 2013 in a political retribution scheme.

The indictments, announced by prosecutors, and the guilty plea by David Wildstein, a Christie appointee to the Port Authority of New York and New Jersey, marked a dramatic downfall for the Christie team. It pushed the scandal back into the headlines at a time when the governor has been struggling to revive his hopes to win the Republican presidential nomination.

Christie got one piece of good news from the prosecutor running the investigation. “Based on the evidence that is currently available to us,” U.S. Attorney Paul J. Fishman said at a news conference, “we’re not going to charge anybody else in this scheme.”

Christie insisted again Friday that he knew nothing of the plot.

“Now 15 months later it is time to let the justice system do its job,” he tweeted.

Fishman said, however, that there were unindicted co-conspirators in the case whom he could not name because Justice Department policy is to not identify people whom the grand jury decides not to indict. But he said those people might eventually be named.

Wildstein’s lawyer on Friday repeated an earlier claim that “evidence exists” that Christie knew about the traffic jam scheme.

Fishman said he could not comment about evidence Wildstein presented because testimony to the grand jury is secret. In saying that no additional charges were pending, “I’m going as far as I believe I can ethically go,” he said.

Even without further charges, however, the scandal over the bridge closings has done huge damage to Christie’s once-high hopes of winning the Republican nomination, moving him from a presumed front-runner to an afterthought. Repeated polls have shown large percentages of Republican voters hold an unfavorable opinion of Christie, and longtime allies of his have increasingly begun backing rival candidates.

Wildstein pleaded guilty to conspiring with the other two — Christie’s former deputy chief of staff, Bridget Anne Kelly, and Bill Baroni, the governor’s top appointee to the Port Authority — during the traffic tie-up scheme that was dubbed Bridgegate. The Port Authority runs the heavily traveled bridge.

Earlier in court, Wildstein, 53, answered “yes” over and over again as Judge Susan D. Wigenton asked whether he had plotted with the others to create massive traffic jams to “punish” the Democratic mayor of the New Jersey city of Fort Lee, at the foot of the bridge, for not endorsing Christie in his re-election bid.

“Public officials must use government resources for proper government purposes,” Fishman said.

The scheme took shape more than two years before it was implemented, according to the indictment, when the three Christie allies began talking about using the lane closures as political leverage against the Fort Lee mayor, Mark Sokolich.

In 2013, as Christie ran for re-election, his team sought endorsements from several Democratic officials in New Jersey in an effort to run up a big victory that had bipartisan support. That could appeal to Republican donors and operatives eyeing Christie for a White House run.

That August, Kelly confirmed that Sokolich wouldn’t be backing the governor, setting the retribution plot in motion.

“Time for some traffic problems in Fort Lee,” Kelly wrote to Wildstein. “Got it,” Wildstein replied.

Wildstein said in court that the lane closures were planned to begin a month later, on the first day of school, to make the punishment especially severe.

“The conspirators concocted and promoted a sham story that reducing the number of lanes and toll booths … was for a traffic study,” the indictment reads. “They created and continually advanced this cover story … to conceal the conspirators’ true punitive purpose.”

Wildstein spoke to Baroni and Kelly the day the closures began, the indictment says, and reported that they had caused widespread traffic problems. Baroni and Kelly “expressed satisfaction” that the plan was working and agreed to continue with the closures, according to the indictment.

As traffic backed up, they also purposely disregarded town officials’ plea for help and requests for information, according to the indictment; the mayor called the situation a “life/safety issue” but was ignored.

The scheme began to unravel as reporters and state lawmakers pressed for more information. After the August emails between Kelly and Wildstein surfaced, Christie fired Kelly.

More than a month after the traffic jams, as Baroni prepared to testify before legislators about them, he tried to distance himself from the traffic study cover story, asking two Port Authority police officers to say police had suggested the study, according to the indictment. The officers disagreed, the indictment says.

The governor has said he knew nothing of the scheme. Last December, state lawmakers investigating the lane closures said they had not turned up evidence that Christie knew of some of his top aides’ plans to create the hellish traffic jams.

Kelly and Baroni each were charged with conspiracy in a nine-count indictment unsealed Friday. It alleges, among other things, that the pair plotted to misuse Port Authority property, conspired to and committed wire fraud, and conspired to injure and oppress civil rights.

In a statement, Baroni’s attorney, Michael Baldassare, called Wildstein a “habitual liar” and claimed Wildstein lied to Baroni, “his close friend of over a decade,” about the traffic study claims. “Bill was given pages and pages of data, emails and documents that would have convinced anyone a legitimate traffic study had been conducted,” the statement said.

Appearing before reporters Friday afternoon, Kelly also maintained her innocence, and called Wildstein a liar. “I never ordered or conspired with David Wildstein to close or realign lanes at the bridge, for any reason, much less for retribution,” she said. “For the indictment to suggest that I was the only person in the governor’s office who was aware of the George Washington Bridge issue is ludicrous.”

Asked what Kelly meant in her text messages to Wildstein, Michael Critchley, declined to comment, saying the answer would come out at trial. Kelly characterized her emails and text messages as “off-handed attempts at sarcasm,” and said she deeply regrets them.

After the scandal surfaced early last year, Wildstein resigned from his senior position at the Port Authority. He pleaded guilty Friday to conspiracy to obtain by fraud or misapply government property, and conspiracy against civil rights. He was released on a personal recognizance bond of $100,000 and is to be sentenced on Aug 6. The maximum sentence he faces is 15 years, but his cooperation with prosecutors was likely to reduce that, Fishman said.

The charges Kelly and Baroni face carry a “theoretical maximum” punishment of 86 years in prison for each of them, Fishman said, but he made clear he didn’t expect either of them to get such a long sentence if they were convicted.

“This is a black eye on representative democracy,” said state Assemblyman John Wisniewski, a Democrat who helped the legislative investigations into the scheme. “People deserve to have the ability to trust their elected officials.”

Los Angeles Times staff writer Joseph Tanfani in Baltimore contributed to this report.

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