 Duffy, a Republican, was appointed Ashland County District Attorney in 2002 by then Governor Scott McCallum, and was reelected unopposed in 2002, 2004, 2006 and 2008.Upon assuming the office of district attorney, he succeeded Michael Gableman, a former justice on the Wisconsin Supreme Court.Duffy was on the Republican slate of the 10 Wisconsin electors for the 2008 presidential election.