Sen. Arlen Specter and Rep. Joe Sestak bitterly attacked each other's character during a televised debate Saturday that was every bit as contentious as their Democratic Senate primary struggle has become in its closing days.

Specter demanded an apology for a Sestak advertisement that calls him a liar and then stayed on the offensive throughout the hour-long debate, pressing several times for Sestak to release Navy records that would explain how the retired admiral came to leave a top Pentagon job.

"I've been in public service for 43 years and no one has ever called me a liar. . . . He's out of bounds, and I want an apology," Specter said.

Sestak did not respond, and ducked the records demand. He said that Specter's relentless attacks were meant to mask his record of supporting the economy-wrecking policies of President George W. Bush.

"Arlen Specter has reverted to his Republican tactics of saying anything to divert attention from what really matters," Sestak said. "Negative attacks have not created one job."

At another point, Sestak compared Specter's tactics to those of Karl Rove, the GOP strategist Democrats love to hate.

Specter, 80, the longest-serving senator in Pennsylvania history, is seeking a sixth term, running for the first time as a Democrat. He switched from the GOP last year after negative reaction to his vote for President Obama's $787 billion economic stimulus made it clear that he would not survive a Republican primary. The White House, Gov. Rendell, the state Democratic Party, and most of organized labor have all endorsed Specter.

Sestak, 58, and a House member in his second term representing Delaware County, bases his campaign on the belief that he is the true Democrat in the race and that the "establishment" should not anoint a senator.

The most bitterly contested point in the debate, as it has been in the advertising of the two campaigns, was the conclusion of Sestak's military service. In an attack ad, Specter's campaign said Sestak was relieved of his post as chief of planning for the Navy because he created a "poor command climate," quoting a 2005 Navy Times article. That account has been confirmed by Pentagon sources speaking to multiple news organizations.

But Sestak denies the report. He says he was pushed out because a new chief of naval operations, Adm. Michael Mullen, wanted his own team and because he had pushed unpopular plans for downsizing the Navy.

Sestak responded with an ad featuring veterans accusing Specter of "swift-boating" the former admiral. "Arlen Specter, don't lie about Joe Sestak's record," one of the veterans says.

Speaking with reporters after the debate, Specter said that the issue was relevant because "his whole campaign is based on his Navy record. . . . It goes to his ability to get things done, to get along with people. He's all peaches and cream on television."

They clashed for an hour in the Fox29 studios on Market Street, likely to be the last encounter between the two candidates before the May 18 primary. Sestak had badgered Specter for as many as six debates - or one in each of the state's media markets - but the incumbent agreed only to Saturday's event. It was sponsored by the Pennsylvania Broadcasters Association and carried live on 14 television stations around the state.

Some outlets will telecast the clash Sunday, including NBC10 at 9 a.m. It will be on C-Span, C-Span Radio, and c-span.org at 7 p.m. Sunday.

Specter and Sestak began squabbling even before the red on-air light came on. Specter began spreading notes on the podium and Sestak objected, saying the rules did not allow notes. The organizer of the debate ruled that Specter could use notes.

They disagreed over the Obama administration's escalation in Afghanistan, with Specter opposed and Sestak, the former military man running from Specter's left, in support.

"Simply stated, [Hamid] Karzai is not a reliable ally – we ought not to be bolstering him," Specter said, speaking of the Afghan president. He said the U.S. should bring about a rapprochement between Pakistan and India so Pakistan can take the fight to al-Qaeda terrorists hiding within its borders.

Sestak said he supported "benchmarks" so that the increase of ground forces in Afghanistan did not become open-ended.

Both candidates said they supported closing a loophole in federal law allowing people to buy firearms at gun shows without a background check, though Sestak blasted Specter for having voted against the assault-weapons ban in the 1990s.

In becoming a Democrat, Specter said he was returning to his roots, noting that former President Franklin Delano Roosevelt was a hero to his family when he was growing up in Depression-era Kansas.

"President Obama took on the tough guys, just as I took on the tea party gang at the town hall meetings," Specter said. "We're going to need a stand-up guy who's used to the rough and tumble of politics to beat [Republican candidate Pat] Toomey."

Contact staff writer Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews.com.