Senate Democrats won a milestone victory early Monday in the health-care debate, approving a procedural motion to move the reform legislation to final passage later this week, and without a single vote to spare.

US Senate Majority Leader Harry Reid speaks during a news conference on December 10 on Capitol Hill in Washington, DC. The White House urged lawmakers to pass contentious health care reform, saying that the watered-down version of a bill before the Senate still accomplishes the president's goals of changing the troubled system.(AFP/Getty Images/File/Alex Wong) The 60-40 tally, taken shortly after 1 a.m., followed 12 hours of acrimonious debate and required senators to trek to the Capitol in the aftermath of a snowstorm. The vote was the first of three procedural hurdles that Democrats must cross before a final vote on passage of the measure, now scheduled for Christmas Eve.

A challenging closing round of negotiations, culminating in a series of compromises with moderates, threatened to overshadow the significance of what Democrats believed they were close to achieving: the most significant health-care legislation since Medicare and Medicaid were created in 1965.

"This bill is the product of years of hard work, study and deliberation," said Senate Finance Chairman Max Baucus (D-Mont.), one of the principal sponsors of the package, in remarks on the Senate floor before the vote. "These are the reforms for which Americans have been waiting."

Not a single Republican voted to advance the measure, including Sen. Olympia J. Snowe, the one GOP lawmaker who had backed an earlier version. The Maine moderate was lobbied heavily by President Obama, but announced Sunday night in a statement that she remained "concerned" about the measure, while objecting to "the artificial and arbitrary deadline of completing the bill before Christmas."

Though admittedly outflanked, Republicans declined to relent. In the hours before the cloture vote, GOP lawmakers took turns condemning the bill in impassioned speeches on the Senate floor. Sen. Lamar Alexander (Tenn.) called it a "historic mistake." Senate Minority Leader Mitch McConnell (Ky.) accused Democrats of producing "a mess" that represented "a blind call to make history."

Sen. John McCain (R-Ariz.), who ran against Obama for president last year, vowed to "fight until the last vote," a threat that could keep senators at their desks until well into the night on Dec. 24.

Senators voted from their desks, a formality observed only for the most important bills. And despite the late hour, the Senate visitors gallery included numerous guests, including Victoria Reggie Kennedy, widow of Sen. Edward M. Kennedy (D-Mass.); Health and Human Services Secretary Kathleen Sebelius; and senior White House aides Jim Messina and Nancy-Ann DeParle.

Obama and Democratic leaders, meanwhile, struggled to contain an uprising on the left. Responding to liberals, who have criticized Senate leaders as caving in on such issues as abortion coverage and the idea to create a government-run insurance plan, the White House and its allies acknowledged in newspaper op-ed pieces and on television talk shows that the $871 billion Senate legislation is not ideal.

But they argued that the measure would transform the health-care system, both for people who have insurance and for 31 million Americans who otherwise would go without.

"This is major reform," White House senior political adviser David Axelrod said Sunday on NBC's "Meet the Press." "It's not perfect. And over time, it may improve," he said.

Senate Democrats prepared for a final round of votes on Majority Leader Harry M. Reid's revised package before sending the measure to a House-Senate conference committee. After a grueling stretch of dealmaking, Reid (D-Nev.) announced this weekend that he had won the support of Sen. Ben Nelson (D-Neb.), giving him the 60th vote needed to overcome a Republican filibuster.

With no parliamentary options remaining, McConnell held out hope that Democrats would stumble in delivering every caucus member to the Capitol at odd hours and after nearly two feet of snow had fallen on Washington.

"People have to show up, and people have to vote. At least three more times," he told reporters. Even if Democrats clear that hurdle, he said, the debate "is not over, by any stretch."

If the Senate approves a bill, negotiations with the House are expected to last into January. The gulf between the House and Senate versions has widened over the past three weeks, as Democratic moderates wary of excessive government involvement in the private sector forced Reid to abandon even the weakened version of the government-run insurance option he tried to add to the Senate package.

Last week, under pressure from Sen. Joseph I. Lieberman (I-Conn.), Reid also scrapped a proposed substitute for the public option that would have extended Medicare eligibility to uninsured people as young as 55. Last month, the House approved a $1 trillion package that includes a government-run insurance plan, and many House liberals want to keep the provision alive to apply competitive pressure to the private insurance industry.

For liberals, a public option came to represent a litmus test for effective reform, a sure way to guarantee that private insurers would face meaningful competition and eventually leading to lower premiums for everyone. But the ideal version of a government plan, one that would pay providers based on Medicare rates, proved a non-starter with many Democrats. And a modified version, with higher rates, was shown by the nonpartisan Congressional Budget Office to hold little appeal, attracting just a few million beneficiaries.

Political reality was slow to take hold. Even in recent days, as the Senate bill broke free of its parliamentary logjam, high profile liberals such as former Democratic chairman Howard Dean, urged Democrats to shelve the Senate effort.

But as White House officials and other top Democrats pushed back, some proponents of the public option urged their allies to take a broader view. "It would be tempting, but it would be wrong" to reject the Senate bill, wrote Jacob S. Hacker, the Yale University professor who first conceived the public-option idea, in an article posted Sunday on the New Republic Web site.

"Since the first campaign for publicly guaranteed health insurance in the early twentieth century, opportunities for serious health reform have come only rarely and fleetingly," Hacker wrote. "If this opportunity passes, it will be very long before the chance arrives again."

Liberal Democratic senators vowed that where the legislation falls short, Congress would answer with modifications and additions. "This is not the end of health-care reform. It is the beginning," Senate health Chairman Tom Harkin (Iowa) said on the floor early Monday. Harkin, who is serving his fifth Senate term, described the procedural motion as "the defining vote of my career."

The House and Senate are at odds over numerous issues, such as how to pay for the initiative and how to bar federal funding for abortion under legislation that would offer insurance subsidies to those who lack affordable coverage through an employer. Nelson, an opponent of abortion, insisted on a provision that would require people who receive the new subsidies to write two checks each month, one for their share of the premium and the other specifically to pay for abortion coverage.

The compromise has infuriated both opponents and advocates of abortion rights. On Sunday, the leaders of the influential House abortion rights caucus, Reps. Diana DeGette (D-Colo.) and Louise M. Slaughter (D-N.Y.), complained that it is "not only offensive to people who believe in choice, but it is also possibly unconstitutional." But other Democrats defended the compromise, urging their colleagues to focus on the broader benefits of the Senate bill.

"This shouldn't be the forum for the debate on abortion," Richard J. Durbin (Ill.), the No. 2 Democrat in the Senate, said Sunday on ABC's "This Week."

Vice President Biden and Victoria Kennedy hit the same themes in op-ed pieces published Sunday, urging advocates of the public option to embrace consumer protections in the Senate bill. Even Dean told NBC's David Gregory that the bill is better now, despite "this last week of unseemly scrambling for votes," and that he would let the measure proceed to conference.

"While it is not perfect, the bill pending in the Senate today is not just good enough -- it is very good," Biden wrote in the New York Times. "I share the frustration of other progressives that the Senate bill does not include a public option," Biden wrote. But he added, "those in our own party who would scuttle this bill because of what it doesn't do seem not to appreciate the magnitude of what it has the potential to accomplish."