If you’re a wavering moderate who’s concerned about the uninsured, then, whatever bill emerges from this month’s negotiations might seem like an opportunity that won’t come round again.

But any legislators voting “yes” should have no illusions about what they’re voting for. This version of reform probably won’t make health care more affordable for most Americans, or place the system on firmer footing for the long run. Despite all the talk about a once-in-a-generation opportunity, our political class will have barely finished congratulating itself before rising costs will force everyone back to the negotiating table to consider more radical approaches.

We know what one such approach would look like. It’s the eventual endgame that liberals pushing a “public option” are aiming for: a federal takeover of the health-insurance sector, paid for by rising tax rates, in which the government guarantees universal access while using its monopoly power to hold down costs.

But there’s another path, equally radical, that’s more in keeping with the traditional American approach to government, taxation and free enterprise. This approach would give up on the costly goal of insuring everyone for everything, forever. Instead, it would seek to insure Americans only against costs that exceed a certain percentage of their income, while expecting them to pay for everyday medical expenditures out of their own pockets.

Such a system would provide universal catastrophic health insurance, in other words, while creating a free market for non-catastrophic care. In the process, it would marry a central conservative insight  that we’ll never control spending so long as Americans are insulated from the true price of their medical care  to the admirable liberal premise that nobody should go bankrupt paying for life-saving treatment.

The details would vary depending on your political predilections. Under the more free-market approach, championed by Harvard’s Martin Feldstein, the government would provide vouchers for the purchase of private catastrophic plans. Under a more liberal version, like the one sketched out by Berkeley’s Brad DeLong, the government itself would act as the insurer. And liberals and conservatives would no doubt disagree about where to set the income threshold, and what additional interventions to support.

The basic outline, though, could find support across the ideological spectrum. The problem is finding champions in Washington, where the political incentives always cut against reforms that fundamentally disrupt the status quo.

DeLong called his vision “an unrealistic, impractical, utopian plan.” For now, he’s right.

But the system can’t continue as it is. Soon, we’ll need reforms that do disrupt the status quo  and a plan that seems unrealistic today might suddenly look like the only sustainable alternative.