It was not the first time Specter had switched parties. The Kansas native and graduate of the University of Pennsylvania and Yale Law School ran for Philadelphia district attorney in 1965 as a Democrat. However, having actually been recruited to run by city Republican Party boss William H. Meehan, Specter switched to the GOP days after his election.
It became clear then that Specter wasn't about to let any party affiliation limit him. He took positions that he believed in. No doubt that fortitude had something to do with his humble beginnings as a Depression baby whose father was wounded in World War I as part of the American Expeditionary Force.
Specter's determination to stand his ground gained national attention when he was asked to be a staff member on the Warren Commission investigating the 1963 assassination of President John F. Kennedy. He held to his theory that a single bullet killed Kennedy and wounded Texas Gov. John Connally despite never being able to prove it.
That same dogged independence was on display when the Republican senator voted with the majority in 1987 to deny President Ronald Reagan's nominee to the Supreme Court, ultra-conservative Robert Bork.
But in 1991, it was liberals who were disappointed when Specter harshly questioned law professor Anita Hill, who had accused another Republican nominee to the court, Clarence Thomas, of sexual harassment. With Specter's vote, Thomas was confirmed.
Specter was a man who could not be bound by labels, a man who never let the odds dampen his spirits, no matter the battle.
He was diagnosed with cancer in 2005. And again in 2008, about a month after his second book, Never Give In, was published. This summer, it was again announced that Specter was being treated for cancer.
In his last book, Life among the Cannibals, Specter spoke out against the partisan divide that has crippled Congress. He said the extremists in both parties were eliminating centrists like him from politics.
"Cannibals devour their young, and that's what happening in Washington," Specter said in an interview recorded for Philly.com. That won't stop, he said, until the vast majority of Americans who are centrists go to the polls in larger numbers.
As Election Day approaches, the best way to remember Arlen Specter is take his words to heart and vote.