Sen. Bob Casey, D-Pa., who served four years with Specter and is seeking re-election as a moderate, said Sunday that he believes moderates can still bring people together.
"It's not going to happen naturally or by accident," Casey said. "Each individual member of Congress has to take on personal responsibility. ... He has to keep the poison out of the water to avoid the kind of demonization that happens when people debate issues."
Specter, Casey said, was one of those people who could disagree without demonizing.
The other two Republicans who supported Obama's stimulus are Maine's two U.S. senators. One of them, Olympia Snowe, announced in February that she wasn't seeking re-election. She said she was frustrated by "'my way or the highway' ideologies."
In one study of congressional polarization, University of Georgia professor of political science Keith Poole mapped the political polarization of Congress by charting votes and found that the parties are more divided than at any time since Reconstruction after drifting further apart in the last 40 years.
Poole said in an essay that there are no true moderates left in the House of Representatives, and just a handful remaining in the Senate, in contrast to the Reagan era when about half of the members of Congress could be described as moderates.
For Specter, the benefit of crossing party lines wasn't always about being true to his convictions. He also used it to benefit the causes he championed.
"He was a master politician," Rendell said. "He was as smart as a whip."
In his 2004 run for re-election, Specter was endorsed by both the AFL-CIO of Pennsylvania and the arch-conservative Rick Santorum, then Pennsylvania's junior senator. Santorum later said Specter had pledged to support then-President George W. Bush's nominees to the Supreme Court, regardless of their views on abortion rights. Specter, who supported abortion rights, had said he never would make such a promise under any circumstance.