The resignation of Port Authority of New York and New Jersey executive deputy director Bill Baroni comes a day after the Democratic National Committee tried to link the controversy to Christie, who is finishing a first term that by New Jersey standards has been scandal-free, and a state lawmaker issued seven subpoenas to Baroni and other agency officials.
Christie, who is shuffling some staff positions as he begins his second term, painted Baroni's departure as an expected move.
"Sen. Baroni offered his resignation and I accepted it, but this wasn't something I hadn't planned already," the governor said. Baroni is a former Republican state senator and insider who was state chairman of John McCain's 2008 presidential campaign and has been Christie's top deputy at the bistate agency for four years.
The new deputy executive director, Deborah Gramiccioni, has a long history of working with Christie, both in the U.S. attorney's office and in his administration. She also worked in the Justice Department in Washington.
The issue at play involves the George Washington Bridge, one of the world's most heavily traveled spans. The town on the New Jersey side of the bridge is Fort Lee, whose Democratic mayor did not endorse Christie in his re-election campaign last month. While Christie is a Republican, his campaign focused heavily on bipartisan support to bolster his image as a pragmatic executive who will work with his political opponents when he needs to.
On Sept. 9, two of the three local-access lanes from Fort Lee to the bridge's upper level were closed without warning. Officials at the Port Authority, the powerful agency that operates the bridge, said the closures were for a traffic pattern study. Christie said Friday that he believes that version of events, though he said Baroni and others did not communicate the plan properly.
Fort Lee officials said they were not informed of the closures in advance. The closures led to gridlock in Fort Lee and were canceled after three days.
The one time Christie previously spoke in public about the issue, he laughed it off.
During a news conference this month, he joked that he personally put up traffic cones to close the lanes. Then he addressed his critics, including two Democratic lawmakers who have been pressing the issue. "Just because John Wisniewski and Loretta Weinberg are obsessed with this," he said, "it just shows you they really have nothing to do."
Christie has cultivated an image as both a blunt, tough-talking politician who takes on such adversaries as public workers' unions and a leader willing to make compromises for the greater good. Democrats have increasingly criticized him for tending to his national image in advance of a possible presidential run - something he has not ruled out - at the expense of taking care of New Jersey issues.
On Friday, Christie blamed Democrats for making too much out of the bridge issue and exploiting "all the other politics swirling around it."
Democratic lawmakers have kept pushing the story by calling Port Authority officials to testify.
Port Authority Executive Director Patrick Foye, an appointee of New York Gov. Andrew Cuomo, a Democrat, told lawmakers that he was unaware of any traffic study.
David Wildstein, the Port Authority's director of interstate capital projects and one of Christie's high school friends, sent a resignation letter last week saying he would leave the agency as of Jan. 1. He said in the letter that he planned to leave anyway in 2014 but was speeding up his resignation because the bridge issue had become "a distraction."
The resignations of Baroni and Wildstein are effective Friday, Christie said.
Baroni earned $290,000 a year as Christie's top deputy, while Wildstein, who was a political blogger under the pseudonym Wally Edge before joining the authority, made $150,000 annually.
Wildstein is a Christie appointee whom others have testified ordered the lane closures.
On Thursday, Wisniewski, the chairman of the state Assembly Transportation Committee and one of Christie's most frequent critics, issued seven subpoenas to access documents and emails related to the lane closures.
On Friday, Wisniewski said he welcomed Baroni's resignation but said that won't put the matter to rest.
"Our investigation into what happened with these lane closings will continue," he said in a statement. "We still don't have an explanation as to what happened here."