After simmering for weeks, the controversy exploded Wednesday when emails and texts emerged to bolster Democrats’ allegations that allies of the New Jersey governor engineered the traffic problems near the George Washington Bridge as part of a political vendetta.

Not that long ago, Christie had mocked questions about the topic. On Thursday, the Republican was apologizing, firing people and denying he had anything to do with the alleged plot.

( PHOTOS: Chris Christie’s career)

So how did it come to this? Here’s POLITICO’s guide:

‘Commuting disaster’

On Sept. 9 in the New Jersey town of Fort Lee, traffic suddenly ground to a halt.

The Port Authority of New York and New Jersey had temporarily closed two lanes from the town to the George Washington Bridge, a major point of entry to New York City, causing massive backups.

John Cichowski, the “Road Warrior” columnist for The Record (N.J.) newspaper, called it a “commuting disaster” that had quadrupled some people’s travel times. An emergency services official said the traffic delayed responses to four medical calls.

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Port Authority officials said the lane closures were part of a traffic study, an explanation Christie said he accepted. But Fort Lee Mayor Mark Sokolich wondered if he was “being sent some sort of message.” Soon, a theory picked up steam: Sokolich was being punished for not joining dozens of other Democrats in endorsing Christie for reelection.

Before long, other New Jersey Democrats were piling on, and multiple reviews of the closures got underway (NJ.com has a detailed timeline.) Christie got reelected, and the controversy stayed largely under the national radar. Until this week.

You’ve got mail

“Time for some traffic problems in Fort Lee.”

Those were some of the bombshell words in documents that emerged Wednesday morning as part of a state lawmakers’ investigation. That line came from one of Christie’s deputy chiefs of staff, Bridget Anne Kelly, in an email to Port Authority official David Wildstein a month before the traffic jam.

Wildstein, a Christie appointee, wrote back: “Got it.”

( Also on POLITICO: Christie’s damage control)

Other messages in the Wednesday trove appeared to disparage the Fort Lee mayor, fueling suspicions that the lane closures were retaliation. Christie canceled a public event and issued a statement, insisting, “What I’ve seen today for the first time is unacceptable.”

On Thursday, Christie faced the press for almost two hours. He apologized, said he was “embarrassed and humiliated,” and denied any involvement in the lane closures.

He said he’d fired Kelly and effectively dismissed another prominent aide named in the messages, Bill Stepien, who had been seen as a potential manager for a 2016 presidential bid. He traveled to Fort Lee and apologized to the mayor in person.

Wildstein — who had resigned from the Port Authority in December as the controversy grew — appeared Thursday before fuming state lawmakers who wanted him to testify. But on his lawyer’s advice, he pleaded the Fifth. The panel slapped him with a contempt accusation.

Staying alive

Even if Christie’s popularity takes a hit inside New Jersey, he is starting from a pretty good position.

He won 60 percent of the vote when he was elected to a second term last November, and 64 percent of likely voters had a favorable opinion of him, according to Quinnipiac — a testament to how he’s made his brash reputation work for him. Plus, any backlash could be offset by people who give him points for how he has responded to the crisis.

Nationally, the governor’s popularity could also take a hit.

( WATCH: Gov. Christie brunt of late-night jokes)

Perhaps the most interesting number to watch on that front is how many people say they have an opinion of Christie rather than no opinion at all (in December, the latter category was 28 percent in a Quinnipiac poll).

Immediate changes to that figure will help explain how much the controversy punched through to a larger audience. But will the effects last through the next presidential cycle? That will depend on what else comes to light in the coming months.

More trouble ahead?

Federal prosecutors are considering whether to launch a full-blown investigation, and state lawmakers will continue their probe. One attorney even filed a class-action lawsuit on behalf of people inconvenienced by the jam.

There will probably be a protracted fight over getting Wildstein to testify, and he might make a play for immunity. The issue is also on the radar of Sen. Jay Rockefeller (D-W.Va.), who leads a committee that oversees the Port Authority.

Thousands more pages of documents were posted online Friday. With news organizations eager to pore over the new material, it’s anyone’s guess how things will shake out in the months ahead.

And if any evidence emerges that Christie himself had a hand in creating the traffic mess, he can probably kiss his 2016 dreams good-bye.