Toomey's popularity among conservatives prompted Specter to bolt the Republican Party in April. Sestak is defying party leaders, including President Barack Obama, by challenging Specter in next May's primary. Both accuse Specter, 79, of flip-flopping on the health care debate.
Anger at Obama's plan to overhaul the health care system has erupted at recent town hall meetings hosted by members of Congress across the country. But questioners at Wednesday's town hall were unfailingly polite, and the audience of nearly 400 listened attentively to the candidates' answers.
There were few sparks, although Sestak's contention that the House version of health care reform will not add to the national debt drew derisive laughter from many.
"Did I part my hair on the wrong side?" he quipped.
Toomey, meanwhile, attracted scattered hisses when he said Medicaid had high rates of infant mortality.
The candidates planned to get together for a beer afterward, borrowing a page from Obama's recent beer summit with a black Harvard University professor and the white police officer who arrested him in his own home.
On the debate stage, Sestak, 57, accused health insurance companies of "cherry-picking" the rich and healthy when deciding whom to cover. He said he favors a government-run insurance option that will force private insurers to compete and offer better service, leading to a system in which "everyone can have health care."
Toomey, 47, said he supports "common sense bipartisan reforms" to rein in spiraling costs and improve access to health care. But he said a "huge government intrusion" into one-sixth of the U.S. economy would prompt employers to stop offering health insurance to their workers, forcing them into the government-run program.
"Do we believe we can't have competitive grocery stores unless we have a government grocery store?" Toomey said.
Toomey lost the 2004 GOP primary to Specter by about 17,000 votes out of 1 million cast. He faces competition for the 2010 Republican nomination from anti-abortion activist Peg Luksik. A Quinnipiac University poll in July showed Toomey neck and neck with Specter in a hypothetical general election matchup.
Sestak is a retired Navy vice admiral from the Philadelphia suburbs who is serving his second House term. Besides Specter, he faces opposition in the Democratic primary from state Rep. Bill Kortz, a former U.S. Steel Corp. manager from western Pennsylvania.
Specter was not invited to participate. He issued a terse statement following the debate: "I look forward to returning to the Capitol next week and speaking to my colleagues about trying to pass a health care reform bill."