WASHINGTON -- Senate Majority Leader Harry Reid yesterday opened debate on his health care reform bill by declaring that the upper chamber will be putting in overtime this month.

"The next weekends -- plural -- we will be working," said Mr. Reid, D-Nev. "There is not an issue more important than finishing this legislation."

Senators yesterday began offering and debating amendments to the bill, an $849 billion expansion of health coverage to tens of millions of Americans, coupled with insurance industry reforms. Mr. Reid hopes for a final vote by Christmas but will need 60 votes to end debate, a considerable task even though his caucus is 60 strong.

Republicans figure to present a near-united front against the bill and will try to draw out debate while magnifying Democratic caucus fractures over two crucial issues: a federal health insurance option and abortion coverage.

Democratic Sens. Ben Nelson of Nebraska, Blanche Lincoln of Arkansas and Mary Landrieu of Louisiana, as well as Connecticut Independent Joe Lieberman, who caucuses with Democrats, have expressed serious concerns about the bill. The only Republican who has shown any potential to support it is Maine's Olympia Snowe, who voted for the Senate Finance Committee version but has said she does not like the current bill's public option.

Pennsylvania's senators, Democrats Arlen Specter and Bob Casey Jr., are not among the targeted centrists, but -- like most senators -- they enter the debate armed with changes they would like to see.

Mr. Specter has proposed an amendment to stiffen penalties for defrauding government health care programs and is considering a pitch for increased National Institutes of Health funding -- long a pet issue for the two-time cancer survivor. He also has expressed concern about proposed Medicare Advantage cuts.

Under the program, private health insurers administer expanded Medicare benefits at greater cost to the government. Kaiser Family Foundation data show that 56 percent of Medicare beneficiaries in the Pittsburgh region are enrolled in Advantage plans, a higher percentage than any other U.S. metro area.

Mr. Casey, who has been focused for months on children's issues, submitted an amendment yesterday to extend the Children's Health Insurance Program through 2019, while expanding enrollment and requiring all states by 2014 to cover children in families up to 250 percent of the poverty line. "No child worse off should be the foundation of what we do in this bill for our children," he said in a floor speech.

Statements and possible amendments from Mr. Casey, an anti-abortion Catholic, will be closely watched. He said that in his view, the current bill does not satisfy existing law that federal money not subsidize abortions. The legislation mandates that at least one plan in a newly created health insurance exchange cover abortions and at least one not cover it.

Another politically sweltering issue -- the government or "public" option -- likely will be hashed out behind closed doors, as leaders try to balance liberals' concerns for a strong public plan to help hold down private insurance costs against centrists wary of further expanding the federal role in health care.

Jim Kessler, vice president for policy at the progressive Washington think tank Third Way and a former staffer for Sen. Chuck Schumer, D-N.Y, said he thinks a compromise will find the requisite votes. "None of those 60 senators are really anti-health reform," he said. ... I don't think there's anyone that says, 'If it doesn't happen, that's fine.' "

Beyond abortion and the public option, the third major controversy is the bill's cost and deficit impact -- numbers that vary depending whether you're looking through red or blue-colored glasses.

The Congressional Budget Office, the nonpartisan financial referee of potential legislation, issued a report yesterday on the Senate bill's effect on insurance premiums in 2016, compared with projections if no action is taken.

The CBO found that premiums would rise 10 percent to 13 percent for those who don't have employer coverage and buy insurance from an exchange or the private market. But those increases would be more than offset by government subsidies to low-income Americans that would make coverage, on average, 56 percent to 59 percent cheaper for that group.

People who receive coverage through small businesses would see premiums stay fairly steady, though when subsidies are factored in, their rates would drop 8 percent to 11 percent. Employees of large firms, who would not qualify for subsidies, would see premium costs decline up to 3 percent.

Democrats declared that the report showed the bill's ability to rein in costs, while Republicans said it showed the opposite, and that it would not do enough to stem explosive growth in health costs.

A Gallup poll released yesterday showed that 49 percent of Americans would prefer that their representatives vote against the health reform bill, while 44 percent want them to support it. These numbers, about the same as a Gallup poll earlier this month, provided further fodder for GOP claims that the public is on their side.

"Americans are fed up with big-government solutions that drive up taxes and debt and which only seem to create more problems, more abuse and more fraud," said Senate Minority Leader Mitch McConnell, R-Ky. "In the face of this, our friends on the other side of the aisle appear determined to plow ahead with their plans. They don't seem to care that Americans are telling them to stop this and start over and fix the problem, which is health care costs."

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.