The only reason the health bill is still under consideration at all is that Barack Obama has more or less staked his presidency on passage of it. Many rank-and-file House Democrats would have walked away long ago if their party leaders had allowed them to do so.

But the president has decided that the only way to get a bill to his desk is by making defeat unfathomable for members of his own party. If the health bill were to go down to defeat, there's no doubt that he would be seriously weakened. It is likely that some House Democrats will support passage simply because they don't want to be responsible for dealing such a crippling blow to the administration.

Still, despite the enormous pressure from the White House, the odds remain against passage, Democratic catastrophe and all.

The votes Speaker Pelosi must get would mainly come from moderates and conservative members elected in highly competitive districts. Their constituents are trending solidly toward opposition to the bill, primarily for cost reasons.

The Congressional Budget Office estimates the new spending and subsidies to expand insurance coverage would add about $200 billion to the federal budget by 2019. Moreover, that new spending would increase at a rate of about 8 percent annually every year thereafter.

Despite assertions to the contrary, the measures designed to offset the additional spending and slow the pace of rising costs are not nearly as robust and certain to occur.

Two key offsets -- the so-called "Cadillac tax" and the permanent cut in inflation payment rate increases for hospitals and other facilities -- generate large savings on paper in the second decade of implementation. But the savings will only occur if a future president and a future Congress are more willing than those in office today to put the squeeze on millions of middle-class families with relatively expensive health insurance and to force large numbers of facilities to leave the Medicare program because of low reimbursement rates.

The public is not naïve. They know government entitlement programs have a strong tendency to grow rapidly once put in place. What they see coming down the pike is another under-financed program, at a time when the federal government is already running up the nation's debt at an unprecedented pace because previous commitments are now unaffordable.

Their concern is well placed, and should be enough to force Congress to come back later with a plan that is less risky for the country's economic future.

James C. Capretta, an associate director at the Office of Management and Budget from 2001 to 2004, is a fellow at the Ethics and Public Policy Center.