(CNN) - The legislative committee investigating the New Jersey bridge scandal has called on one of Gov. Chris Christie's top political advisers to cooperate with its probe.
The Select Committee on Investigation has subpoenaed Michael DuHaime, a prominent Republican strategist who served as a top adviser to Christie's 2009 election and last year's re-election.
The legislators want him to hand over a broad range of documents, including anything related to orchestrated traffic jams last September in Fort Lee.
The gridlock was caused by the sudden closure of access lanes to the George Washington Bridge over several days, and investigators are looking at whether the whole thing was politically motivated.
The issue has called into question Christie’s forceful governing style, and clouded his potential 2016 presidential candidacy.
"The subpoena is part of the committee's continued, bipartisan investigation into the lane closings and apparent abuse of government power," the panel said in a statement on Wednesday.
The subpoena appears to stem from comments DuHaime made to investigators hired by Christie’s office to look into the saga.
Memos released by Gibson, Dunn & Crutcher, the law firm that headed up the internal review that cleared Christie of any wrongdoing, revealed that DuHaime met with a key figure in the scandal, David Wildstein, at a coffee shop in November.
Wildstein was a top Christie appointee at the Port Authority of New York and New Jersey, which oversees bridge operations. It’s been alleged that he carried out the lane closures.
According to one memo, DuHaime told investigators that Wildstein said it was his idea to close the lanes for a traffic study.
Democrats leading the investigation appear to be digging further into Christie's political operation.
The subpoena calls for DuHaime to hand over calendars, notes and other communications related to the lane closures.
It also requests documents related to Christie, his former campaign manager, Bill Stepien, staff from the Port Authority and the governor's office, and Christie's former deputy chief of staff, Bridget Kelly. It was Kelly who has been identified as writing the now-infamous email to Wildstein weeks before the lane closures: "Time for some traffic problems in Fort Lee."
CNN reached out to DuHaime for comment and is awaiting his response.
The same committee on Tuesday heard oral testimony for the first time from a former Christie staffer who worked under Kelly.
Christina Renna, who worked in the governor's Office of Intergovernmental Affairs, depicted Kelly as a difficult manager who was overwhelmed and not always good at making decisions.
Renna told the committee that while Kelly played an "instrumental" role in the lane closings, she doubts Kelly thought it up.
Kelly's lawyer responded Wednesday, saying Renna's portrayal of her as "insecure, erratic and paranoid is completely at odds with Ms. Kelly's 20-year record serving in state government."
Kelly herself has waged a successful legal campaign to blunt the committee’s subpoena for information.
Next week the committee is scheduled to hear subpoenaed testimony from Michael Drewniak, Christie's chief spokesman.
Christie has said he knew nothing about the traffic jams until after they occurred.
The U.S. Attorney’s office has separately empaneled a grand jury as part of its investigation.