In Washington, it is an accepted, cyclical reality that, after a major bill on a large government program is enacted, the bill's subject matter is off-limits for at least four or five years, and usually longer. The recently enacted Medicare prescription drug bill was in the works for half a dozen years, and it was the most radical revamping of the health care program for seniors since the program's creation in 1965. Major parts of the bill don't even go into effect until 2006 and 2010.

To be sure, many members of Congress would be thankful for a respite from the heated Medicare debate. Both Republicans and Democrats are still getting an earful from graying constituents who aren't satisfied with the prescription benefit. Many conservatives, for their part, are reeling at the high price tag of the large new government entitlement (the White House estimates $534 billion over 10 years) and are angry that the Bush White House apparently knew the cost before congressional Republicans reluctantly promised their votes.

Yes, a break from Medicare would surely be welcome.

But any respite will be very brief, warn two of Medicare's six trustees -- John L. Palmer, professor of economics and public administration at Syracuse University, and Thomas R. Saving, director of the Private Enterprise Research Center at Texas A&M University. Both are finishing four-year terms as trustees; Palmer was a Democratic choice, and Saving a Republican pick. Palmer expects that the new Medicare law will force Congress to consider another major Medicare bill within just two or three years.

  The reason is that the new prescription drug law includes a trigger mechanism that kicks in if costs get too high. If total Medicare costs start to exceed the money that is set aside for the program under various Medicare trust funds, and an escalating share of general tax revenues has to be directed toward paying for the program, the trigger activates. Specifically, if Medicare's trustees project in two successive years that, at some point in the next seven years, general government revenues must be tapped to pay for 45 percent or more of total Medicare costs, the president has to submit "corrective" legislation to Congress. The House would be required to act under a "fast-track" procedure, but Senate rules on filibustering would still apply. In other words, the new law does not guarantee that a corrective bill would pass, but the president and Congress would at least have to take a hard look at the problem and start working on potential solutions.

Palmer estimates that the trustees may fire off the first of the two warnings as early as next year, or in 2006. If so, Medicare could again be the center of attention in Washington by 2006 or 2007. But next time, the debate won't center around what the government can give seniors. It will be about how to keep Medicare from eventually bankrupting the entire federal government.

"The trustees found that our obligations to future retirees are unfunded by a staggering $62 trillion. Add that to an earlier estimate of unfunded liabilities for the Social Security pension system, and the figure rises to $72 trillion," Sen. Joe Lieberman, D-Conn., said in a recent Financial Times editorial. "It is hard for most people to grasp those astronomical figures," he wrote. "They far exceed the entire net worth of the United States. But, as a nation, we must urgently grasp them -- and act. Americans cannot afford to ignore this reality. Each year that we do nothing, this 'entitlement gap' will grow by $2 trillion."

In March, Medicare's trustees, including Palmer, Saving, and the secretaries of Health and Human Services, Labor, and Treasury, released their annual report detailing the financial status of the Medicare and Social Security programs. The stark conclusions for Medicare went way beyond the bad news that Medicare's hospital insurance trust fund would go broke in 2019 -- seven years earlier than the trustees predicted last year.

The trustees' assessments have typically measured the viability of the trust fund, and that's what prompted a few days' worth of scary headlines back in March, before the public's focus returned to the prescription benefit and the war in Iraq. But the worst news in the report was Medicare's cash-flow problem -- what the government has to pay out every year in general revenues for the program, apart from what is in the trust funds -- and that got very little attention, say Palmer and Saving. Lieberman was one of a tiny minority on Capitol Hill to speak up.

Here's why the trustees argue that Washington and the public should be focused on Medicare's cash flow, and not on the trust fund. The trustees explain that the hospital insurance trust fund, which is part of Medicare Part A -- the part that pays hospital bills for seniors -- is merely a government authorization to pay out money. There's no actual cash in the fund. When Part A has a surplus, it is accounted for in the fund, sort of like an IOU, but the actual cash goes to the Treasury as general revenue and gets spent on other government programs. So, when Medicare Part A has a deficit year, it can't just fill out a withdrawal slip and tap into the surplus that it has accumulated. It must ask the Treasury to pay back its IOU in general revenues. But because the surplus money has already been spent, the Treasury then has to figure out where to get the money.

This year, for the first time, Medicare will have to draw on general revenues to cover spending -- about $4 billion worth. "The Treasury either has to come up with the money or cut some other program," Saving said in an interview. It helps that Social Security is projected to have a surplus this year. But Palmer and Saving say that both programs will soon run deficits, and the problem of where to find cash will worsen.

Medicare has several components, including Medicare Part A (hospitalization), which is financed primarily by payroll taxes paid by workers and employers. Part B (doctor services) and Part D (the prescription drug benefit) are financed primarily by transfers from the general revenues of the Treasury, and by premiums that beneficiaries pay. Revenue that is not needed to pay benefits and related expenses is held in the hospital insurance and supplementary medical insurance trust funds, and invested in U.S. Treasury securities.

Palmer and Saving have used their roles as trustees over the past few years to try to educate Congress and the public to focus more on Medicare's broad cash-flow situation, and less on the status of the trust funds. And this year's report is no exception. Right up front, the trustees note that Medicare expenditures were 2.6 percent of the nation's gross domestic product in 2003. And "in 2006, with the implementation of the new prescription benefit, total expenditures are estimated to be 3.4 percent of GDP. The figure is expected to increase rapidly to 7.7 percent by 2035 and to 13.8 percent by 2078," according to the trustees' report.

Saving is about to release a report through the National Center for Policy Analysis, where he is a fellow, that expands on this picture. The funding deficit in Medicare this year is equal to about 3.6 percent of federal income taxes, he writes. "In less than five years, the share of income taxes needed will double, and five years beyond that, it will double again," according to Saving. By 2019, the federal government will need more than one of every four income-tax dollars to pay benefits to the elderly in Medicare and Social Security, in addition to dedicated revenues already set aside for the two programs.

The problem worsens dramatically as Baby Boomers retire, and it doesn't improve much after they've exited the programs. By 2030, about midway into the Boomer retirement years, half of all federal income-tax revenues will need to go toward deficits in Social Security and Medicare, Saving writes. And by 2070, "the elderly will need all federal income taxes, in addition to all payroll taxes and premium payments, leaving nothing to pay for any other federal program."

The new Medicare law, at an estimated cost of as much as $534 billion over just the first 10 years, worsens the program's financial difficulties. Already this year, physicians, hospitals, and health plans are receiving more-generous reimbursements from Medicare. Then, in 2006, the expensive prescription benefit kicks in.

So why has the trustees' report received such scant attention? It garnered only a few days of news reports, which focused primarily on the premature exhaustion of the hospital trust fund. And why has there been so little screaming from Capitol Hill? Lawmakers knew even before the trustees' report that the new Medicare law would make the situation dramatically worse.

John Goodman, president of the National Center for Policy Analysis, says the federal government is reluctant to focus on the problem. He experienced that unwillingness firsthand when the trustees' report was set to be released in March. The trustees had planned to issue their findings with just a news release and no fanfare, Goodman said. Then, when the numbers were found to be so "devastating," Goodman decided to arrange a news conference, which he announced in an e-mail. After that, he said, the federal government scheduled its own news briefing for one hour before Goodman's. He says that didn't leave enough time for reporters to get to his event.

Assuming that members of Congress had some idea about the problem, why didn't they do more to address Medicare's cash-flow deficit in the new law? It's all politics, said Palmer and Saving. "The administration, given that they pushed the Medicare bill, didn't want to make it seem like everything is really expensive," said Saving. "And Democrats want to pretend there isn't a problem. If neither wants to talk about it, then there's not much news, even though these numbers are so staggering. And it has gotten below the radar with other things going on. Maybe it will surface after the election, once the prescription benefit really kicks in."

But even if Congress steps up to the plate, solutions won't come easily, said Palmer. "The magnitude of the problem is so much greater" than with Social Security, he said. "You can't deal with it in isolation like Social Security, because it's so deeply embedded in our whole health care system. If you make sure [Medicare] only grows to a certain level, and you screw down on provider reimbursements, for example, then that affects everyone down the line.... I don't think there's anybody now who could say with confidence, 'Here's what we need to do. Here's how we solve it.' "

The only way that Congress was able to pass a Medicare prescription drug bill late last year was to avoid that discussion, Saving said. However, he added, Congress won't be able to put it off much longer.