The bridge in question, George Washington Bridge, in 2016. (Photo by Drew Angerer/Getty Images)

A judge just opened the door for New Jersey prosecutors to investigate whether to charge New Jersey Gov. Chris Christie (R-N.J.) with a crime in relation to Bridgegate. But it's not clear prosecutors would even go down that road.

Still, this is a newsworthy development for a governor who has long maintained he did not know anything about closing lanes of one of the world's busiest bridges for 5 days in 2013, apparently in an act of political retribution against a local mayor. So let's dig in.

On Wednesday, a New Jersey judge decided to allow a complaint of misconduct filed by a local activist to go forward, which means the judge essentially handed the complaint over to New Jersey prosecutors to decide what to do with it.

Christie has, for years — and as recently as Tuesday — denied he knew anything about the lane closures that snarled the New York and New Jersey area on the first week children were back in school three years ago.

“The simple fact is the Governor had no knowledge of the lane realignments either before they happened or while they were happening,” Brian Murray, a spokesman for the governor, told NBC New York. “This matter has already been thoroughly investigated by three separate independent investigations.”

But even a hint of possibly being charged with criminal wrongdoing is not good news for Christie. Whatever political ambitions he may have had after his failed presidential run and his term as governor ends in 2017 may have already been crushed thanks to a really bad 2016. Joining the Donald Trump administration has been on the table — he's chairman of Trump's transition team right now — but the Republican nominee would first have to win.

Now, there's at least the possibility — however remote — that Christie could be indicted for the scandal that has come to define him. And in an absolute worst, worst-case scenario, he could face jail time.

Here's what you need to know about the latest Bridgegate developments.

Where are we now in Bridgegate fallout?

Some of Christie's former allies have long said Christie knew about the lane closures. Two of his top former aides are on trial right now related to it. Another pleaded guilty in relation to closing the lanes. Their attorneys argue Christie knew about the closures and made them scapegoats to protect his 2016 presidential ambitions.

But September, as the New York Times' Kate Zernike reported, was the first time we heard prosecution say they also think Christie knew:

The prosecutor, speaking for the United States attorney’s office, said that two of the alleged co-conspirators in the case, David Wildstein and Bill Baroni, had “bragged” to the governor about the lane closings at a memorial service for the Sept. 11 terrorist attacks, on the third day of the closings, and that they had been done to “mess” with Mayor Mark Sokolich of Fort Lee, a Democrat, because he had declined entreaties to endorse the governor’s reelection.

If Christie knew, why wasn't he charged?

The answer isn't really clear; Zernike reported that merely knowing is not a crime.

Other investigations have cleared him. In 2014, lawyers — working for Christie — completed a review and came to the conclusion Christie wasn't involved.

Then, there's the question of how to even charge him. The Asbury Park Press reports Bridgegate is a difficult case to prosecute because there was no obvious quid pro quo. The bridges were closed months before an election where Christie won by a landslide despite the Fort Lee mayor, a Democrat, refusing to endorse him. And those allegedly involved didn't get any money, cars or favors for doing it.

What happened in the trial of Christie aides?

It's still going on. (Bridgegate is a complicated nest of political personalities and ambitions, he-said, she-said finger-pointing and government bureaucracy. It takes a while to unravel. Here's a refresher.)

But the developments aren't good news for Christie. On Tuesday, a lawyer for Christie's former deputy chief of staff, Bridget Anne Kelly, said Kelly told Christie about the lane closures before they happened and the week they were happening. Kelly is the second former aide to say Christie was informed about the closures.

Regarding that trial, Christie has said if he were served with a subpoena, he would testify. That hasn't happened yet.

What happens next for Christie?

It depends. Could be nothing, or he could be charged with a crime; it would probably be misusing his public office. The Bergen County Prosecutor's office now faces whether there is enough evidence to put the case before a grand jury, who in turn would decide whether to indict Christie.

Or that could not happen at all. Prosecutors' offices have wide discretion on whether to pursue a case, said James Cohen, a criminal law expert with Fordham Law School. “The prosecutor is under no obligation to do anything at all, nor is the prosecutor barred in any way from digging up the kitchen sink and throwing it at Christie.”

Politics are also likely to play a role, Cohen said. Charging a sitting governor with a crime is a lot of work and will require prosecutors to meet a high legal standard of proof. Prosecutors will be looking at whether the evidence on Christie rises to that occasion. But they're also likely to factor in the ongoing trial of Christie's two aides.

If prosecutors decide to pursue a misconduct charge, and if a grand jury decides there's enough evidence, it could go to trial. And — we're firmly in hypothetical land here — IF Christie is found guilty related to misusing his public office to commit a crime (what crime, we're not sure because no one has charged him with one), he could face jail time. New Jersey's misconduct law says a public servant who commits a crime in office could face up to 10 years in jail.

But that's a lot of ifs to get to jail time. Right now all we know is the door is at least opened for prosecutors to charge Christie with a crime related to Bridgegate.