PITTSBURGH — Nine months before they will square off at the ballot box, Sen. Arlen Specter (D-Pa.) and Rep. Joe Sestak (D) greeted a civil and largely friendly crowd Friday morning when they separately made their cases to the annual meeting of liberal bloggers and interest groups known as the Netroots Nation.Specter, who switched parties in April and has spent most of his career fending off attacks from the conservative right wing of the GOP, now finds himself courting left-wing groups like the ones gathered here as he faces a primary challenge from Sestak.But it was Sestak, whom liberal bloggers supported in his first bid for Congress in 2006, who clearly had more visible support among the convention participants.Specter tried to make his case to the progressive crowd, repeatedly citing his decades-long relationships with Vice President Joseph Biden and Pennsylvania Gov. Ed Rendell (D). He said he became a Democrat when he voted for President Barack Obama’s economic stimulus package, although he did not officially change parties until two months after the vote. “Without my vote on the stimulus, Philadelphia and the state would be in much, much worse shape,— Specter said. The audience was skeptical, to say the least, but certainly warmer than some of the angry crowds Specter had spoken to earlier in the week at health care town halls across the state. He recalled the anger that he had witnessed at these town halls, including overhearing what he perceived as death threats to Members of Congress at a town hall earlier this week in Lebanon, Pa. “I’m out there fighting for President Obama’s health care plan, and nobody in the Democratic caucus has been out there with four town-hall meetings,— he told the crowd. “I mean nobody has done it.—When asked to comment on Sen. Chuck Grassley’s (R-Iowa) public comments on the advance directives in the health care reform legislation, Specter said he would call his colleague to tell him that his view was simply “not correct.— When a few Members of the audience chanted “call him now,— Specter obliged. “Whoever said that, join me backstage and watch me dial him,— Specter said.The crowd, which included Rep. Carol Shea-Porter (D-N.H.), appeared to be more supportive of Sestak, who has been a darling of many progressive bloggers during his two campaigns for Congress. An energetic Sestak greeted the crowd without a suit jacket and with his sleeves messily rolled up. He repeatedly told the expansive ballroom filled with bloggers that he ran for Congress because he wanted everyone to have the great health care that his family — including his daughter who was diagnosed with a brain tumor at an early age — had when he was in the military. “The principles of the Democratic Party, which I consider practical or progressive, are what I got in for,— Sestak said. Sestak acknowledged that the town hall crowds he has greeted have been much more civil than others across the state, including Specter’s well-publicized events. He excitedly described the reaction, boasting that he shook every hand at the two town halls he has done in the Keystone State. “That’s America,— he said with a chuckle after the forum. “And here’s the problem, I honestly believe: I don’t think we’ve done a good job out there explaining it.—