A leading Democratic senator’s decision to release his long-awaited health care overhaul bill Wednesday with no Republicans on board dims the chances for a bipartisan compromise on President Barack Obama’s top domestic priority.

Sen. Max Baucus, the Senate Finance Committee chairman, insisted Tuesday that he’ll keep negotiating with the three Republicans and two fellow Democrats who’ve been in closed-door talks with him for months on the bill he was to reveal Wednesday. Mr. Baucus said he hopes that by the time the committee votes on the bill, as early as next week, Republicans will be there.

But for now, despite numerous gestures to Republicans, Mr. Baucus has fallen short in his quest to assemble a coalition of senators from both parties behind his proposal. Mr. Obama also hoped for bipartisan support behind plans for reshaping the $2.5 trillion U.S. health care system to hold down costs and cover the uninsured.

“The door’s always open -- always hoping that somebody, all six, will be on the bill,” Mr. Baucus told reporters Tuesday evening after the latest meeting of his so-called Gang of Six senators. “We’re just going to keep the door open, keep working, keep discussing.”

Mr. Baucus’ panel is one of several congressional committees that have been working on the health care overhaul, but it is seen as the only one with a prospect of reaching an agreement with Republicans.

Mr. Obama had campaigned on a pledge of bipartisanship and has said he wants to reach a compromise with Republicans on a health care package. Liberal Democrats, though, doubt Republicans can be persuaded to support any agreement and want Mr. Obama to use his party’s strong majorities in both chambers to push through legislation.

But it is not clear that he has the votes to do so. Democrats are now one vote shy of the 60 votes they need to block Republican efforts to derail the bill in the Senate. Also, with congressional elections approaching next year, some Democrats from conservative states are wary about supporting an overhaul that voters may see as too liberal.

The United States is the only major industrialized country without a comprehensive health care plan, leaving nearly 50 million without insurance to cover costly medical bills. Most Americans have private insurance through their employers and some buy their own policies. The government covers the elderly, disabled and indigent.

Many of the details in Mr. Baucus’ bill were already known. Unlike more liberal versions passed by three committees in the House and by the Senate’s Health Committee, it shunned liberals’ call for the government to sell insurance and relied instead on co—ops to offer coverage in competition with private industry.

Mr. Baucus’ approach includes a requirement for individuals to buy insurance, with financial penalties for those who don’t. Rather than a mandate for larger businesses to provide coverage for employees, they would be required to defray the cost of any government subsidies for which their employees would qualify.

The bill is expected to cost about $880 billion over 10 years, and it tracks closely with the goals Mr. Obama laid out in his speech to Congress last week.

In an opinion piece published Wednesday in The Wall Street Journal, Mr. Baucus bemoaned the “misinformation” about his proposal and wrote, “The reality is that our plan controls spending without adding to the federal deficit, expands coverage, protects consumers from unfair insurance industry practices, and puts choice back into the hands of consumers and businesses.”

Mr. Baucus has been working for months with his committee’s top Republican, Sen. Chuck Grassley, along with Republican Sens. Mike Enzi and Olympia Snowe. In the end, Democrats believe Snowe may be the only one to support the bill, though she wasn’t committing to that Tuesday night.

“Hopefully at some point through the committee process we can reach an agreement,” she said.

Enzi said he was not yet ready to declare his position. Grassley applauded Mr. Baucus’ effort at bipartisanship, but contended that Senate Democratic leaders and the White House had imposed an “artificial deadline” on the negotiators and those Democratic leaders “haven’t made a commitment to back a broad bipartisan bill through the entire process.”

“It looks like we’re being pushed aside by the Democratic leadership so the Senate can move forward on a bill that, up to this point, does not meet the shared goals for affordable, accessible health coverage that we set forth when this process began,” Grassley said in a statement.

He cited Republican concerns over cost, taxpayer funding for abortion services, medical malpractice lawsuits and subsidies for illegal immigrants in any health care bill.

Even as Mr. Baucus has failed to win over Republicans, he also faces opposition from liberals on his committee. Some of them want a public plan in place of co-ops, and several have also expressed concerns about whether Mr. Baucus, in his effort to keep his bill’s price tag down, has done enough to make health coverage affordable for working-class and low-income Americans.

“The way it is now there is no way I can vote for the package,” Sen. Jay Rockefeller, a Democrat, said Tuesday on a conference call with reporters, becoming the first Finance Committee Democrat to voice outright opposition.

Release of Mr. Baucus’ bill sets the stage for what could be a lengthy and contentious drafting and voting session to begin next week, with numerous amendments expected both from the right and from the left. Following that, Democratic leaders in the House and the Senate are aiming for floor action in the fall.

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