Arlen Specter, the former Pennsylvania senator whose switch from Republican to Democrat ended a 30-year career in which he played a pivotal role in several Supreme Court nominations, died Sunday, his family said. He was 82.

Specter, who announced in late August that he was again battling cancer, died at his home in Philadelphia from complications of non-Hodgkins lymphoma, his son Shanin told the Associated Press. Over the years, Specter had fought two previous bouts with Hodgkin's disease, overcome a brain tumor and survived cardiac arrest following bypass surgery.

Specter gained fame in the 1960s as an aggressive Philadelphia prosecutor and as an assistant counsel to the Warren Commission, developing the single-bullet theory that posited that just one bullet struck both President Kennedy and Texas Gov. John Connally -- an assumption critical to the argument that presidential assassin Lee Harvey Oswald acted alone, the AP noted. The theory is still controversial after 49 years.

Specter was first elected to the Senate as a Republican in 1980. In 1987, he helped thwart President Ronald Reagan’s Supreme Court nomination of Judge Robert H. Bork, bringing him conservative enemies. But four years later, he angered liberals with his tough questioning of Anita Hill at Clarence Thomas' Supreme Court nomination hearings and by accusing her of "flat-out perjury."

In 2004, Specter barely survived a Republican primary challenge by conservative Rep. Pat Toomey. He went on to easily win the general election with the help of organized labor and many Democrats.

Specter startled the Senate in April 2009 by suddenly when he announced he was switching to the Democrats, saying he found himself "increasingly at odds with the Republican philosophy." Earlier that year, he had been one of only three Republicans in Congress -- and the only one facing re-election in 2010 -- who voted for President Barack Obama's economic stimulus bill.

By 2010, Specter, who had already battled cancer, was Pennsylvania's longest-serving senator when Rep. Joe Sestak challenged him from the left in the Democratic primary, despite Specter's endorsements by President Barack Obama and other party leaders. Sestak defeated Specter but lost the seat to Toomey by 2 percentage points.

Over his career, Specter frequently changed his political leanings and often split his votes between Democrats and Republicans, angering colleagues on both sides of the aisle, The Wall Street Journal noted. He generally supported affirmative action, some gay-rights protections and abortion rights — while saying he personally opposed abortion. But he strongly opposed most gun-control measures.

Later in his career, Specter switched sides twice on a bill to ease union organizing, finally telling labor unions in 2009 that he backed the measure.

In an autobiography that came out earlier this year, Specter again bemoaned the increasing polarization of Washington and primarily faulted his former GOP colleagues and the rise of tea party activists. "Politics is no longer the art of the possible when senators are intransigent in their positions," he wrote.