Sen. Arlen Specter during a 2006 interview. (Wikimedia Commons)

The official cause of death was complications of non-Hodgkins Lymphoma. He was 82.

Specter's career highlights include a reputation for his "fierce independence" on the Senate floor, putting forward the "single-bullet theory" in the assassination of former President John F. Kennedy and grilling Anita Hill during the confirmation hearing for Supreme Court nominee Clarence Thomas on her allegations of sexual harassment (we're using "highlights" loosely here).

But for all his controversial moves, Specter was also known for his willingness to cross the aisle—a disposition that eventually lead him to leave the Republican Party in 2009 and switch his registration back to Democrat. 

Read more about his long career here, and more of Neon Tommy's Senate coverage here. 

Reach Executive Producer Catherine Green here. Follow her here.