THE rise of popular democratic movements in Eastern Europe changes East-West geopolitics almost daily. In the Soviet bloc, what previously seemed impossible - socially, politically, economically - begins to seem possible. Freedom is proving to be a powerful elixir. Hard-line nations realize they may need to soften. East Germany continues to allow the technically illegal New Forum socialist opposition party a hearing - and it is gaining adherents not only in major cities, but in smaller towns as well. Czechoslovakia and Bulgaria face new forms of dissent to which they are partly accommodating.
Perhaps the most surprising development in this new world is Moscow's recent hint that Hungary is free to leave the Warsaw Pact. Hungary has proven to be the East bloc's most radical reformer. Last week it declared itself an independent republic. It wants to move closer to the free-market West. But disengaging from the Warsaw Pact has so far been an idea entertained mainly by extremists in Budapest.
What Moscow's hint may say, partly, is that Mikhail Gorbachev, with his own tremendous domestic ethnic and economic problems, has to let Hungary go. East-bloc nations are discrete entities. Mr. Gorbachev can allow Hungary positions he couldn't grant East Germany. Beyond that, no one knows what is in the ``fine print'' of Moscow's offer - first proposed by two Soviet spokesmen on US television. Hungary is a model nation for Gorbachev, having reformed from within the party. A free-market Hungary would be an example of successful perestroika.
Yet even if ``allowed,'' it may not be wise for Hungary to leave the Warsaw Pact now. It is easy to get caught up in the euphoria of reform. But at the moment, political freedom in Hungary exceeds economic ability. No country has ever switched from a Stalinist to a Western economy. There may be shortages, instability, and confusion. To withdraw too quickly from the Pact may leave Hungary vulnerable to backlash if reforms falter. Hard-liners could exploit the situation. This is a present concern for the struggling Solidarity-led Mazowiecki administration in Poland.
Of course, a more pro forma role for Hungary in the Warsaw Pact, leading to withdrawal and nonaligned status, would be welcome. Toward that end, Hungary's ongoing practice of grass-roots democracy is essential. The free flow of people, ideas, commerce, and exchange - free press, speech, elections - all will continue to expand and develop. The announcement this week of a referendum in November and a presidential election in January is a good sign. So are indications that Gorbachev will remove Soviet troops.
The European Community's help will be critical. Bonn is offering the Poles $1 billion in loan credits; the French, $650 million.
For now, Hungary can accomplish its goals within the Warsaw Pact. Budapest is pulling out of a hydroelectric project with the Czechs, for example. Gorbachev's risk needn't be Hungary's.