HARRISBURG, Pa. (AP) — Arlen Specter, a pugnacious and prominent former moderate in the U.S. Senate who developed the single-bullet theory in President John F. Kennedy's assassination and played starring roles in Supreme Court confirmation hearings, lost a battle with non-Hodgkin lymphoma at a time when Congress is more politically polarized than anyone serving there — or living in America — can remember.

Specter, 82, died Sunday, after spending much of his career in the U.S. Senate warning of the dangers of political intolerance.

For most of his 30 years as Pennsylvania's longest-serving U.S. senator, Specter was a Republican, though often at odds with the GOP leadership. His breaks with his party were hardly a surprise: He had begun his political career as a Democrat and ended it as one, too.