The government’s key witness in the George Washington Bridge lane-closing case said that he interpreted an email from one of the defendants that it was “time for some traffic problems” as an order to put a political revenge plot into action.

David Wildstein worked for the Port Authority of New York and New Jersey, the agency that operates New York-area bridges, tunnels, ports and airports. He pleaded guilty last year to conspiring to cause traffic gridlock near the bridge to punish Fort Lee’s Democratic mayor for not endorsing Republican Gov. Chris Christie.

Bridget Kelly, Christie’s former deputy chief of staff, has claimed the email from mid-August 2013 was a joke, but Wildstein testified Monday that he didn’t take it as one.

“I understood that to mean it was time to change the lanes configuration at the upper level of the George Washington Bridge in order to create traffic in the borough of Fort Lee,” Wildstein said. “We had had joking emails before. I did not think she was joking.”

The government contends that a month later, Wildstein, Kelly and Port Authority executive Bill Baroni put the plan into action and caused four days of traffic jams.

Baroni and Kelly are on trial for fraud, conspiracy and civil rights counts. Christie hasn’t been charged, but prosecutors say Wildstein will testify that he told the governor about the plot on the third of the four days of traffic chaos. Christie has denied that.

Both defendants say Wildstein conceived and carried out the scheme in September 2013. The bridge, one of the world’s busiest, spans the Hudson River and connects Fort Lee, New Jersey, with New York City.

Last week, Wildstein testified that Christie’s office used the Port Authority as a source of political favors for local Democratic officials whose endorsements were sought for his 2013 re-election. Christie wound up winning easily.

Wildstein said Christie and his former campaign manager, Bill Stepien, were among those who discussed the strategy at a meeting about Christie’s re-election.

Stepien and another former Christie aide who testified Friday, Matt Mowers, now work for Republican presidential nominee Donald Trump’s campaign.

Kelly and Baroni have pleaded not guilty and have said the government has twisted federal law to turn their actions into crimes. They also have said other people with more power and influence were involved in the lane closures but aren’t being prosecuted.

Wildstein also testified he told Stepien about the lane closures in mid-August 2013, shortly after his email and discussion with Kelly, and told Stepien he was going to “create the cover of a traffic study.”

Mowers, a former Christie campaign staffer who worked with Kelly in early 2013, testified last week that Kelly’s office kept a spreadsheet noting what favors mayors had received and, on a scale from 1 to 10, their likelihood of endorsing Christie.

Prosecutors say Fort Lee Mayor Mark Sokolich, one of the Democratic mayors who declined to endorse Christie, was the target of the traffic jam scheme in September 2013.

(AP)