Chris Christie is facing another 'scandal that just won't die'

United Airlines CEO Jeff Smisek's resignation, which was announced Tuesday, could cause headaches for the presidential campaign of New Jersey Gov. Chris Christie.

Christie saw his poll numbers and standing in the Republican primary field plummet as he faced "Bridgegate" and three former officials linked to the governor's administration were hit with criminal charges.

The scandal involved lane closures on the George Washington Bridge that were allegedly ordered as part of a plot to exact revenge on a mayor who didn't endorse Christie's 2013 reelection bid.

In May, prosecutors announced that they did not expect further "Bridgegate" indictments, but Smisek's exit from United is linked to another set of allegations involving some of the same erstwhile Christie allies.

When the airline announced the departure of Smisek and two other executives Tuesday evening, it released a statement that said the changes were "in connection with the company's previously disclosed internal investigation related to the federal investigation associated with the Port Authority of New York and New Jersey."

This federal probe involves accusations United lavished Christie and his associates with cash, dinners, and even a special plane route as the airline sought lower fees and funding for its operations at Newark Airport in New Jersey.

An operative for a rival GOP presidential campaign gleefully predicted the new developments in the airline scandal would add to Christie's woes.

"He's already run millions of ads and done numerous town halls that have gotten him nowhere in the polls. Now he has to contend with yet another new story of a scandal that just won't die," the operative said.

The most salacious aspect of the airline scandal is the so-called "chairman's flight."

According to Bloomberg News, in September 2011, Smisek had dinner with David Samson, a Christie appointee who was chairman of the Port Authority. That agency oversees Newark Airport and the George Washington Bridge.

At that dinner, Bloomberg reported that Samson complained to Smisek that he was upset United had canceled a direct flight from Newark to Columbia, South Carolina, because he used the route to visit his vacation home.

Bloomberg reported that Samson asked United to reinstate the route, which subsequently became known at the airline as "the chairman's flight."

United again canceled the route from Newark to Columbia in early 2014, three days after Samson resigned from the Port Authority amid the growing "Bridgegate" scandal. After Samson's departure, the Port Authority rejected United's push for lower fees. As part of the federal investigation, prosecutors have subpoenaed records relating to the South Carolina flight.

Samson and the Christie campaign did not immediately respond to requests for comment. United's statement about Smisek's resignation said the federal probe is continuing.

"The investigations are ongoing and the company continues to cooperate with the government," the statement said.