While majority Democrats will need 60 votes again to finish, some in the party say they'll jump ship from the bill without tighter restrictions on abortion coverage. Others say they'll go unless a government plan to compete with private insurance companies gets tossed. Such concessions would enrage liberals, the party's heart and soul.
There's no clear course for Senate Majority Leader Harry Reid, D-Nev., to steer legislation through Congress to the president's desk. You can't make history unless you reach 60 votes, and don't count on Republicans helping him.
But Reid is determined to avoid being remembered as another Democrat who tried and failed to make health care access for the middle class a part of America's social safety net.
"Generation after generation has called on us to fix this broken system," he said at a recent Capitol Hill rally. "We're now closer than ever to getting it done."
His bill includes $848 billion over 10 years to gradually expand coverage to most of those now uninsured. It would ban onerous insurance industry practices such as denying coverage or charging higher premiums because of someone's poor health. Those who now have the hardest time getting coverage - the self-employed and small businesses - could buy a policy in a new insurance market, with government subsidies for many. Older people would get better prescription coverage.
Most people covered by big employers would gain more protections without major changes. One exception would be those with high-cost insurance plans, whose premiums could rise as a result of a tax on insurers issue the coverage.
The public is ambivalent about the Democrats' legislation. While 58 percent want elected officials to tackle health care now, about half of those supporters say they don't like what they're hearing about the plans, according to a new Kaiser Family Foundation poll.
The Senate debate risks alienating more people because much of the discussion probably will revolve around divisive issues that preoccupy lawmakers.
"A large portion of the debate will be spent on issues that aren't important to the workability of health reform," said Paul Ginsburg, president of the Center for Studying Health System Change.
The debate should start off modestly, with each side offering one amendment. No votes are scheduled Monday.
Reid wants to finish by Christmas; he may not get to.
Of the many issues senators have to weigh, abortion funding and the option of a government insurance plan promise to be the most difficult.
On abortion, no compromise seems possible. On the public plan, a deal may yet be had.