Former U.S. Sen. Arlen Specter, who embodied dying breed of liberal Republicanism switching to the Democratic Party at the twilight of his political career, died after a lengthy battle with cancer, his family announced Sunday.

Specter died of complications from non-Hodgkins Lymphoma on Sunday morning at his home in Philadelphia, his family said. He was 82.

The veteran Pennsylvania senator had overcome numerous serious illnesses over the past two decades, including a brain tumor and non-Hodgkins lymphoma. He had been in the public eye from the 1960s, when he first gained attention as a member of the Warren Commission.

Specter was elected to the Senate in 1980 and represented Pennsylvania in that chamber longer than anyone in history.

All along, his politically moderate image fit hand-in-glove with the politically blue Northeast, both its Democratic centrists and its liberal Republicans.

He had long been one of America's most prominent Jewish politicians, a rare Republican in a category dominated by Democrats over the decades.

His name is synonymous with Pennsylvania, an idiosyncratic state that pushes and pulls between the two parties, and his home, the staunchly Democratic city of Philadelphia.

"One of the few true wild cards of Washington politics," a 2006 article in Philadelphia magazine called him, "reviled by those on both the right and the left."

"Charming and churlish, brilliant and pedantic, he can be fiercely independent, entertainingly eccentric, and simply maddening," the article said.

G. Terry Madonna, director of the Franklin & Marshall College Poll and professor of pubic affairs at Franklin & Marshall College, said Frank Sinatra's song "My Way" could apply to Specter.

"There isn't any doubt in many respects he was an unusual politician," Madonna said. "He didn't look at polls. He didn't track how his comments were playing out in the press. ...

"He was fundamentally a pragmatist who could bend with the times," Madonna said, and he believed greatly that government could help people.

"The Republicanism in his day, it was a different kind of Republican. He was a Philadelphian, and not into that staunchly conservative Republicanism that we see" today.

Madonna called Specter an "indefatigable" public figure, very demanding of both himself and those who worked for him over the years. He had a few election losses but he was undeterred by defeat, the prospects of losing and the challenges he faced.

"The last thing you would have thought about Arlen Specter was that he was born in Kansas," Madonna said. "He always came across as kind of urbane. He had a kind of caustic sense of humor."

But Specter in fact was born in Wichita, the youngest child of Lillie Shanin and Harry Specter, an immigrant from Ukraine. He grew up in Russell, Kansas, also the hometown of another Republican icon, a one-time presidential nominee and senator, Bob Dole.

After graduating from Russell High School in 1947, Specter first went to the University of Oklahoma. But he eventually went east for his higher education. He earned a bachelor's degree in international relations in 1951 from the University of Pennsylvania, in Philadelphia, where he graduated Phi Beta Kappa.

He was in the U.S. Air Force during the Korean War from 1951 to 1953, serving as a second lieutenant in the Air Force Office of Special Investigations. He returned to his studies and graduated from Yale Law School in 1956.

After Yale, he started practicing law and became an assistant district attorney in Philadelphia.

He served on the Warren Commission, which investigated the assassination of President John F. Kennedy in 1963, at the recommendation of Rep. Gerald Ford.

He is credited with co-authoring the "single bullet theory," which suggested that some of the wounds to Kennedy and then-Texas Gov. John Connally were caused by the same bullet.

Even though he was a registered Democrat, Specter ran successfully for Philadelphia district attorney on the Republican ticket in 1965 and eventually registered as a Republican. He lost an election for Philadelphia mayor in 1967.

He served as district attorney until 1974 and prosecuted corruption cases against Philadelphia magistrates and Teamsters.

Specter ran for the U.S. Senate in 1976, but was defeated in the Republican primary by John Heinz. He ran for governor but was defeated by Dick Thornburgh in the primary.

But he won his bid for Senate in 1980, and distinguished himself, serving until 2011.