THE ONLY CERTAINTY in Russia's present crisis is that it marks the end of an era - the Yeltsin years for sure and quite probably the end of the theory, widely trumpeted just a decade ago, that market democracy has triumphed as a universal ideal.

In 1991, it was clear that communism in Russia was going to collapse. And there seemed to be little debate that Russia and all post-Communist states would follow the Western norms in some form. But now it's impossible to foresee the shape of a post-Yeltsin Russia.Why? Let's look at our three previous models for understanding post-Communist Russia, all of which are now being trotted out.

The first model, market democracy, has been advocated by the Clinton administration and the International Monetary Fund with the support of all Western European governments.

Namely, "reform" means a transition to market democracy through price liberalization, privatization and a stable ruble. In due course, these policies, their advocates predicted, would restructure Russia along Western lines.

President Boris Yeltsin, for all his faults, was deemed indispensable to this policy, for he alone could defend reformers against the forces of resurgent nationalism and neo-communism.

Yet Russia's liberal experiment has now collapsed in a spectacular and completely unexpected fashion, leaving the country both bankrupt and without a government - in a sense, in worse straits than after communism's collapse.

These events have given greater credibility to the second model, one that embraces a market economy with a welfare state more expansive than any in the West. Supporters of this model have long charged that a quick turn to a strict market economy was inappropriate to both Russian national tradition and post-Communist conditions.

Forcing Russia into a market economy, in this view, was to turn over, at fire-sale prices, the nation's industries and natural resources to the old nomenclature and to new robber barons, while dilapidating the savings and pensions of vulnerable citizens, especially the elderly.

The second model, however, has never been tried in pure form. In the mid-1990s, voters in Poland and Hungary, hurting from the turn to a new liberal economy, returned Communists to the leadership. Adam Michnik, a leader in Poland's Solidarity Party, called the elections a "velvet restoration."

The Communists added an affordable safety net to the prosperity generated by Poland's liberal "shock therapy" of 1990, the first cold-turkey transition to capitalism, which was highly successful. In other words, the second model could work only if economic liberalization had already generated the needed money.

A third model, advanced especially in Socialist and academic quarters, is more radical than the second. According to this theory, Mikhail Gorbachev had already made the transition from Stalinist communism to a market social democracy. Real reform, therefore, should have continued on that course until "Socialism with a human face" was reached at last.

In this perspective, Yeltsin was a spoiler, who turned to unbridled capitalism and ruined the country. This model is a fantasy whose time has passed: The Hungarian and East German Communist regimes tried it in 1989 and 1990, and it led to their demise.

In practice, however, the liberal West could support only a liberal market democracy for Russia. Now that this course has collapsed, we are left with no effective model for making sense of Russia's predicament.

Still, at first it seemed as if the liberal model might work for Russia, which did try to make a real transition to a privatized economy, however diluted by barter and riddled with corruption. At the same time, freedom of expression and elections, however manipulated by the business oligarchy, have been accepted as the norm. And the younger generation of Russians, in the cities if not in the countryside, has become genuinely attached to these principles. Moreover, the 20th-century record overall is clear: In the long run, there does exist a distinct correlation between free markets and free politics.

So why did the Yeltsin-IMF course end in the present debacle? Why was the Yeltsin regime unable to collect taxes, to pay wages, to regulate its banks and to finance its debt? Surely, this was not the result of faulty fiscal and monetary policy alone. The deeper reason is the legacy of the leviathan Soviet state, which when it collapsed left behind only administrative and economic rubble, devoid of the judicial, accounting and police procedures necessary for a modern society.

So what might emerge from Russia's rubble? There will certainly be a significant swing away from free markets to a statist economy - not a complete return to communism but something more radical than the "velvet restoration" of Eastern Europe. And this new course will last a long time, perhaps a matter of years.

Unfortunately, there is no realistic alternative. The liberal Western model has failed - maybe not because of its inherent flaws, but to most Russians that doesn't matter. The post-Communist experiment has failed nevertheless. And after a somber, low-key summit, it's clear that a devalued American president and a defeated Russian president can hardly stem this tide.