Vice President Dick Cheney’s former chief of staff pleaded not guilty Thursday in the CIA leak scandal, marking the start of what could be a long road to a trial in which Cheney and other top Bush administration officials could be summoned to testify.

I. Lewis “Scooter” Libby entered the plea in front of U.S. District Judge Reggie Walton, a former prosecutor who has spent two decades as a judge in the nation’s capital.