Complex sentence: Edwards handpicked his protege, John Breaux, to run as his successor, who held the seat for 15 years before being elected to the U.S. Senate for the first of three distinguished terms in which he became one of the nation's most influential legislators.
Split into simpler sentences: Edwards handpicked his protege, John Breaux, to run as his successor. Breaux held the seat for fifteen years before being elected to the U.S. Senate for the first of three terms in which he became one of the nation's most influential legislators.