Day 5 of the health reform debate continues on the Senate floor, but the real work is getting done behind closed doors, where moderate and liberal Democrats, and a few moderate Republicans are trying to find a reform plan that will get 60 votes. My colleague on Capitol Hill, ABC's Z. Byron Wolf, is following the story: The tensions were on display Friday at a “tripartisan” press conference called to highlight moderate Senators’ cooperation in creating a battery of amendments, but which turned into a debate on the merits of a public health insurance option between Independent Joe Lieberman of Connecticut, who caucuses with Democrats, Democrat Arlen Specter of Pennsylvania and Republican Susan Collins of Maine. Lieberman reiterated his pledge to filibuster the Democrats’ bill if a public option is not stripped, calling a public option a “foot in the door” to a single payer, government-run health care system. Collins agreed, pointing to the failure of Dirigo, a public health insurance option set up in Maine to insure more than 100,000 Mainers without insurance, but which now insures around 10,000, she said. Specter, a former Republican seeking reelection to the Senate as a Democrat who supports a “robust” public option, asked to offer a rebuttal to Lieberman and Collins at the press conference with them and said the government has learned lessons from Dirigo. The three have crafted a battery of amendments they say would improve Democrats’ bill by, among other things: quickening the pace for a pilot program to bundle Medicare payments to doctors and hospitals, creating a continuum of more effective care, stiffening penalties for hospitals that incur the most infections among patients, and creating a streamlined rating system for doctors. Lieberman and Collins, at the outset of the press conference, said the bill, as written by Senate Majority Leader Harry Reid with pieces from bills passed earlier this year by two committees, has good elements. “The bill may look so good that Sen. Lieberman might able to make some accommodations,” said Specter, to laughter from Lieberman. But don’t look for accommodations any time soon. Lieberman was asked if compromise public option language being crafted by Sen. Tom Carper of Delaware, could gain his vote. “I respect Tom Carper and he is a dear friend,” said Lieberman. “But the answer is no.” Lieberman said he hopes Democrats will drop the public option soon because the debate has turned from an attempt to improve health reform to an attempt to come to a political compromise. Collins said Carper had called her twice in recent weeks, including the day before Thanksgiving, to court her support, but she would not be swayed. “This is a philosophical difference so it is not easily compromised,” she said. The same could be said of abortion rights, another hot button issue in the health reform debate, but not at this press conference. Collins, Lieberman and Specter, all who support abortion rights, all also support language in the bill as written by Reid that would restrict the use of public funds for abortion services. Some Democrats, including Sen. Ben Nelson of Nebraska and Sen. Bob Casey of Pennsylvania, who want to stiffen Reid’s language to more closely resemble language written by anti-abortion rights Democrat Rep. Bart Stupak, D-Mich. That language would further restrict abortion services to people receiving subsidies to buy health insurance and passed in the House of Representatives version of health reform.