Though originally and finally a Democrat, he spent his long career as an elected Republican, though his party label never predicted his policies or his views.
He supported abortion rights, gay rights, affirmative action and the 2010 health-care reform act.
But he also supported gun rights, opposed same-sex marriage and helped scuttle health-care reform in 1994.
Both sides? I'll say.
He always said he took one issue at a time and dealt with each thoughtfully, not ideologically. Who does that now?
And no other politician in the history of the nation could have accomplished what Specter did in 2004 and 2010: in '04, he was endorsed for reelection by President Bush; in '10, he was endorsed for reelection by President Obama.
Specter could be maddening in his positions.
He angered the right by opposing President Reagan's nomination of Robert Bork to the high court in 1987 and earned the moniker "Benedict Arlen."
He angered the left by tough interrogation, many said sexist bullying, of Anita Hill during now-Justice Clarence Thomas' hearings in 1991, and helped create "The Year of the Woman" in American politics.
And during the Senate impeachment trial of President Clinton, he declined to vote yea or nay, instead citing Scottish law and voting "not proven."
Yet he survived all this, plus brain tumors and a heart-attack.
What a mix he presented.
Throughout his career he was known as a media hound and hard to work for.
He used Senate committees for attention-getting hearings on issues such as sex, violence and kids, and called headline-grabbing witnesses as diverse as Captain Kangaroo and Linda "Deep Throat" Lovelace.
Washington magazine once offered a survey of Capitol Hill staffers that rated him the Senate's "meanest" member.
Yet he loved humor and doing stand-up comedy.
And he was known - though given too little credit - for doggedly pushing medical research from the time he entered the Senate in 1981, and including time as chairman of a key appropriations subcommittee.
In Specter's first Senate year, the annual budget for the National Institutes of Health was $3 billion. By '04, it was $28 billion. Today it's $30 billion-plus.
Of all the things government spends on, medical research has to be among the most important.
Overall, what consistently struck me about Specter was a rare combination, for any politician, of high intelligence, amazing endurance and warrior-like will.
Many pols are smart. Many are tireless. Almost none are smart and tireless.
Dozens of Arlen stories demonstrate such qualities.
He visited the state's 67 counties constantly (and was always more than willing to name them), whether during election years or not. He conducted mind-numbing public meetings, one after another.
No other candidate could show up at a local political dinner without learning that Specter was either there or on the way.
And yet he was thoughtful and moderate in a party and profession that increasingly seemed to value neither trait.
He also was someone who could have been or done anything. An Ivy League (Penn) Phi Beta Kappa and Yale lawyer, he didn't need politics to provide a livelihood.
He chose public life as a career. And he had one like no other.
Contact John Baer at firstname.lastname@example.org. For his recent columns, go to philly.com/JohnBaer. Read his blog at philly.com/BaerGrowls.