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WASHINGTON -- The future shape of the U.S. health-care system could hang on the uncertain health of one very prominent American.

Sen. Edward Kennedy, chairman of the Health, Education, Labor and Pensions committee and a senator for more than 45 years, has championed health-care issues his whole career. But he has been fighting brain cancer and working on the legislation long distance from his Massachusetts home. Meanwhile, Sen. Max Baucus, chairman of the Finance Committee, is crafting a bill of his own that could set legislation on a different path.

If the liberal Mr. Kennedy takes a lesser role, that could make it easier for the more-conservative Mr. Baucus to push the health-care legislation in a centrist direction. Mr. Kennedy, for example, is a major proponent of including a publicly run health-insurance option as part of a plan to give all Americans coverage, while Mr. Baucus is weighing other proposals that wouldn't include such an option right away.

Mr. Kennedy's committee late last week began circulating the first draft of its proposal for sweeping changes, starting the maneuvering in earnest. The committee is scheduled to hold a "markup" -- public sessions to make final the bill's details -- in mid-June.

Following that, Mr. Kennedy's committee will engage in intensive negotiations with Mr. Baucus, chairman of the Senate Finance Committee. Then the Democrats must guide the bill to passage on the Senate floor.

On Saturday, President Obama devoted his weekly radio address to the issue, saying that fixing health care is "a necessity we cannot postpone any longer."

Republicans are stepping up criticism of some of the principles outlined by Messrs. Obama and Kennedy. And Iowa Sen. Chuck Grassley, a Republican who is working with Mr. Baucus on his bill, delivered a jab to the president in a Twitter posting after the radio address. "You got nerve while u sightseeing in Paris to tell us 'time to deliver' on health care," Mr. Grassley wrote. "We still on skedul/even workinWKEND."

Navigating the egos of the Senate and guiding bills to passage is a task at which Mr. Kennedy excels. Yet at this long-awaited moment, it isn't clear whether Mr. Kennedy can be on the scene to direct the effort. A spokesman declined to discuss his health or schedule.

"As Senator Kennedy has said many times, guaranteeing that all Americans have access to affordable and quality health care is the cause of his life," the spokesman said. "He's been a leader on this issue for 40 years, and he continues to lead. That doesn't depend on location." Mr. Kennedy stays in contact with staffers and fellow senators from his home.

The draft of Sen. Kennedy's bill calls for guaranteed access to health insurance for all Americans and would require employers to help provide coverage or pay a penalty if they don't. It would end the practice among insurers of denying coverage to people on the basis of pre-existing health conditions, and it would set up new state-run exchanges through which people could comparison shop for coverage. The draft doesn't say precisely how the government would pay for the changes.

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