MOSCOW, JULY 5 -- Before Mikhail Gorbachev came to power, Soviet leaders were accustomed to measuring progress toward communism in five-year cycles, neatly demarcated by Communist Party congresses. At the 21st Congress in 1961, Nikita Khrushchev even made the rash promise that the final phase of full communism would be achieved in time for the party's 26th Congress in 1981.

Communism, needless to say, was not achieved by 1981 -- and its fruition has now been relegated to the indefinite future. But the old idea of Communist Party congresses as landmark events in Soviet history has somehow lingered -- and not just in the minds of Kremlin propagandists. When the 28th Party Congress opened here this week, a year ahead of schedule, Dan Rather, Tom Brokaw and Peter Jennings were in Red Square to record the proceedings.

So how important is the Soviet party congress? Or, to put the question another way, how much political influence does the Soviet Communist Party still wield at a time when its rating in public opinion polls has slipped to single digits, when new political parties are springing up every week and huge chunks of the country have declared their right to overrule the Soviet Constitution?

Some political observers here maintain that what is at stake in the heated debates now underway in the Kremlin is not the future of the Soviet Union, but the future of the Soviet Communist Party. The party, according to this argument, has been overtaken by the larger political and economic forces unleashed by Gorbachev and now faces an uncomfortable choice: It must either adapt or perish.

"You should not exaggerate the significance of the congress in the life of the country," said Moscow's new mayor, Gavril Popov, reflecting the views of many radical politicians. "If the Communist Party was the only executor of perestroika, as it was five years ago, the congress would play a huge role. But today, the situation is entirely different. The fate of perestroika is being determined by the logic of history, which no one can abolish."

Many Soviets clearly agree with Popov. The stock reaction of most Muscovites to the 28th Party Congress has been a big yawn. State-run television has given up the gavel-to-gavel coverage normally reserved for such events and is broadcasting only edited summaries. The country's most popular Communist, Boris Yeltsin, has not bothered to attend most of the debates, presiding instead over sessions of the Russian republic's legislature across town.

Several prominent reformists on the outgoing party Politburo have indicated that they have no particular wish to belong to what used to be regarded as the inner sanctum of Kremlin power. Foreign Minister Eduard Shevardnadze told the congress this week that he believes senior government officials should not also occupy high party posts. Another Gorbachev ally in the Politburo, Alexander Yakovlev, has said he wants to concentrate his attention on the new presidential advisory council.

It is, however, too early to write off the party. Its influence may have declined as a result of Gorbachev's perestroika reforms, but it remains immense. Through its network of cells in every single institution in the country, its 2-billion-ruble budget and its control over the bureaucracy, the party wields enormous power.

"I wish that what Popov says about the party was true, but for the time being the party still determines the fate of the country," said Anatoly Sobchak, an energetic lawyer elected last month as mayor of Leningrad. "The most important organs of state power -- the police, the army and the KGB -- are still in the hands of the party."

Sobchak complained that the Leningrad branch of the KGB still submits daily reports on the political and industrial situation in the city to the local Communist Party chief while refusing to provide the same service to the elected soviet, or city council. In theory, the party boss has no right to be receiving such reports at a time when executive power has been transferred to the soviets. But old habits apparently die hard.

The party apparatchiks may be in a minority in the city councils of Leningrad, Moscow and other big cities, but they still control most of provincial Russia, enabling them to block any reform legislation adopted by the Russian republic's new legislature. Most factory managers also belong to the nomenklatura, the list of party-approved officials selected for high-flying careers.

In an attempt to create an alternative power base, Gorbachev got himself elected earlier this year to the new post of executive president. But he is well aware of the danger of allowing the party to slip from his grasp. His supporters are doing their utmost to ensure that he is reelected general secretary of the party at the end of the congress, even if it means taking a conservative as his deputy.

The Communist Party, in effect, operates as a state within a state, with nearly 300,000 activists and workers on its payroll. Its property -- valued at nearly 5 billion rubles ($8 billion at the official rate of exchange) -- includes 114 publishing houses, 16 higher party schools and hundreds of special hospitals and rest homes. The resources available to rival political parties are minuscule in comparison.

The drama of this week's congress is that a majority of delegates seems determined to prevent the party from either perishing or adapting to the new political environment. Speakers who suggested that the party needed to change itself profoundly, including the reformist Moscow Communist Party chief, Yuri Prokofiev, were drowned out by a slow clapping of hands, a uniquely Soviet way of showing disapproval. The government's chief economic adviser, Leonid Abalkin, received similar treatment when he predicted that the party would be swept from power if it resisted a transition to a free market.

Judging from its opening sessions, the congress is likely to conclude its work next week by electing a predominantly conservative leadership under Gorbachev. That will set the stage for a power struggle between the reformist-controlled government councils and the conservative-controlled party. The radicals will have the right to propose, but the hard-liners will have the power to dispose.