Complex sentence: Meehan went on to serve as Special Counsel to Senator Arlen Specter, and later as campaign manager for Senator Rick Santorum, Philadelphia District Attorney Ron Castille, and State Attorney General Ernie Preate.
Split into simpler sentences: Meehan went on to serve as Special Counsel to U.S. Senator Arlen Specter. He was a campaign manager for U.S. Senator Rick Santorum, Philadelphia D.A. Ron Castille, and State Attorney General Ernie Preate.