Prosecutors have also been looking into allegations by the mayor of Hoboken that the Christie administration withheld relief money after Hurricane Sandy, to pressure her to approve a project by a developer represented by Mr. Samson’s firm.

If indictments touch only the people Mr. Christie dismissed from his orbit because of the scandal, he is likely to argue that the federal inquiry affirms his version of the events, and that he made the necessary corrections.

They would include Bridget Anne Kelly, the deputy chief of staff who sent the “traffic problems” email; and Bill Stepien, the governor’s campaign manager and his pick for chairman of the state’s Republican Party.

Image Bridget Anne Kelly, a former deputy chief of staff to Mr. Christie, was fired for her role in the lane closings at the George Washington Bridge Credit... Pool photo by Chris Pedota

Mr. Christie might make the same argument about David Wildstein, the Port Authority official who received the email from Ms. Kelly and ordered bridge workers to close the lanes, and Bill Baroni, the deputy executive director at the authority, who testified before the Legislature that the closings were part of a traffic study — an argument discredited by bridge officials two weeks later. Mr. Baroni and Mr. Wildstein resigned before the scandal erupted in January 2014; Mr. Christie bathed them in praise and said their departures had nothing to do with the closings.

If Mr. Samson is indicted, it will be harder for Mr. Christie to shake the taint of corruption. And the details that come out of any indictment or trials could reinforce what critics have long said of him: that he fostered a culture in which political bullying was acceptable if not encouraged; that whether or not he planned the lane closings or knew about them as they happened, it was the kind of caper his staff knew would please him.

Testimony to the Legislature made clear that the Christie administration and the Port Authority purposely ignored Mr. Sokolich’s calls, emails and texts during the closings inquiring whether they were intended to punish him. It was only by mistake that a staff member in Mr. Christie’s office picked up a call from Mr. Sokolich. He relayed the mayor’s complaints to his boss, who relayed them to Ms. Kelly in an email that indicated that the administration had been trying to ignore the mayor.