WASHINGTON — Arlen Specter, the irascible senator from Pennsylvania who was at the center of many of the Senate’s most divisive legal battles — from the Supreme Court nominations of Robert H. Bork and Clarence Thomas to the impeachment of President Bill Clinton — only to lose his seat in 2010 after quitting the Republican Party to become a Democrat, died Sunday morning at his home in Philadelphia. He was 82.

The cause was complications of non-Hodgkin’s lymphoma, his son Shanin said. Mr. Specter had previously fought Hodgkin’s disease and survived a brain tumor and heart bypass surgery.