MOSCOW -- Behind Boris Yeltsin, newly reticent as the Communist Party's Congress convened, are surging forces in the Soviet Union that can truly transform this country.

Yeltsin, one of 4,700 Communist delegates, was impassive as first-day proceedings droned on. When a reporter asked his opinion of Mikhail Gorbachev's report, Yeltsin waved the question away with a hand gesture, seeking to distance himself from a decaying institution.

The Soviet Communist Party, even after abdicating its Leninist-Stalinist dominance in running the country, remains massively unpopular. Resignations of membership, once coveted as the ticket for success, may exceed 1 million (about five percent). Gorbachev's attempts to humanize this party of place-seeking bureaucrats (''socialism with a human face'') generate sneers from the people.

If military and security forces do not provoke disaster by intervening, the future will be contested between social democrats (led by such newcomers as Leningrad Mayor Anatoly Sobchak and Moscow Mayor Gavril Popov) and free-market conservatives. The latter comprise the true engine of radical change for not only democracy but capitalism, a broken-up Soviet Union and unilateral nuclear disarmament. These reformers look to Boris Yeltsin to lead them.

This is the same Yeltsin who has not turned in his Communist card, calls himself a social democrat and in his autobiography still expressed misgivings about private property and multiparty democracy. But like this country itself, the new president of the Russian Republic is speeding along a fast track of change unimaginable months ago.

Indeed, it would have been hard to imagine the new Russian politicians who see Yeltsin as their leader -- such as Arkady Murashev, a 32-year-old non-Communist scientist who defeated three Communists for election to the Supreme Soviet from Moscow. Secretary of an influential caucus of reform delegates, he sees 72 years of Bolshevism as a tragic mistake whose wreckage must be cleared away.

Murashev's idol is Margaret Thatcher, and American conservative activist Paul Weyrich is his friend and tutor. He and his wife Olga, who runs a private charity, are both children of Communist military officers and were raised without religion. But each was baptized last year.

Murashev's parliamentary group opposed Gorbachev's treatment of Lithuania, and he wants a loosely federated Soviet Union (''like the European Community''). He sees no military threat from a united Germany, much less the United States, and talks about Soviet ''one-sided'' nuclear disarming.

Can Yeltsin travel this visionary path? It hardly seemed possible last year after his visits to the United States and Western Europe were fiascoes. Reported drinking bouts and incoherent proclamations seriously impaired his image in the West.

A reputation for instability persists because of incidents such as one here last weekend. Yeltsin was personally committed to do a televised interview with us to be broadcast internationally over CNN, but, without warning, failed to show. When aides cited vague ''health'' reasons and called his appearance ''a physical impossibility,'' the worst suspicions were aroused.

One political ally later told us the no-show stemmed from Yeltsin's desire to say nothing about Gorbachev's efforts in the Party Congress to revive a discredited instrument of power. If so, his discourtesy to us reflects a new self-discipline.

Whatever his faults, Yeltsin is seen by reformers as capable of taking the radical steps needed and demanded by the Russian people. Gorbachev cannot even attempt rudimentary market mechanisms, pandering to the hard-line congress majority by pledging to continue on with the proven failure of collective farms. While Gorbachev promises recession and inflation without legal reform, Yeltsin preaches a free market without austerity.

That helps explain the Bush administration's enduring embrace of Gorbachev, which so puzzles reformers here. U.S. policy makers seem wedded to the idea that pain is essential for economic improvement, and prescribe shock treatment for people made lazy by the false promise of a Communist free lunch. While these Americans view and fear Yeltsin as a populist demagogue, he in fact is emerging as the leader of Russians who want democracy, capitalism, religion and demilitarization. Gorbachev cannot follow that agenda, but Yeltsin may try.