NEWS ANALYSIS : Soviet Party’s Fortunes Likely to Keep Sliding : Communists: Gorbachev wants them to be society’s ‘vanguard.’ But a reformer likens them to the Titanic’s passengers.

Summing up the efforts of the Soviet Communist Party to reinvent itself, one skeptic said all he and his almost 4,700 comrades at the party congress have been doing is pouring “new gasoline into an old engine.”

A leading Soviet reformer, Moscow Deputy Mayor Sergei B. Stankevich, said the Communists meeting in the Kremlin seem as oblivious to impending doom as passengers on the Titanic arguing over what music the orchestra should play.

For two weeks, the 18-million-member party headed by President Mikhail S. Gorbachev has refashioned its mission and its leading institutions in a bid to retain its waning appeal and clout under the country’s budding multi-party system.

Gorbachev said the party, now shorn of its constitutional right to rule, should make itself into society’s “vanguard force.” But it is highly unlikely that the 28th Party Congress, which is scheduled to end today, will accomplish anything of the kind.

Although an official assessment should come today, Alexander N. Yakovlev, a Gorbachev ally who wants out of the Politburo, seemed to predict a continuing slide in Communist fortunes by noting disapprovingly that “the party of the revolutionary idea has turned into the party of power.”

In a search for “consolidation” of his party’s forces, Gorbachev impressively reasserted his control over traditionalists and conservative functionaries. But with the dramatic resignations of the wildly popular Boris N. Yeltsin and members of the Democratic Platform group from the congress Thursday, he lost a piece of the left wing whose support he had been courting to counterbalance the right.

As if to underline how fragile the party’s once-unchallenged mandate to govern has become, miners across the country struck for a few hours Wednesday to press assorted political demands, including the end of nearly 73 years of unbroken Communist rule.

This party congress has been a “completely different ballgame” because it is the first since 1925 at which genuine debate has been permitted, said Adam Ulam, director of the Russian Research Center at Harvard University. In fact, the specialist on Soviet history and politics noted, the 28th congress “was almost a brawl.”

Such heartfelt arguing may not have helped the party’s cause.

“The important thing is that no matter how decisions have been made, the party every day is losing its importance in connection with the political and economic life of the country,” Ulam said.

Significantly, many of the delegates who came from around the country to the Kremlin Palace of Congresses kept bringing up the fate of their Communist comrades in Eastern Europe, and some were clearly worried about coming to a similar end.

Pro-reform Communists expressed fears as the congress began July 2 that conservatives would rout Gorbachev and make inroads into his program for perestroika , or national restructuring. But Gorbachev imposed himself and his handpicked deputy, Vladimir A. Ivashko of the Ukraine, and after a remodeling of institutions, arguably became more powerful inside the party than ever.

“The election of the general secretary without meaningful control from the Central Committee, with no right to recall him, plus his powers as Soviet president--this is a gigantic accumulation of powers in the hands of one man and very dangerous,” said Alexander V. Buzgalin, a member of the Marxist Platform group that advocates “pure” Marxism.

As well as altering the balance inside the party, the congress changed the distribution of power between the party and the government. Final decisions on key issues such as the party’s new statutes should come today, but it is already clear that a post-congress textbook on Soviet politics will show that:

Responsibility over key sectors is being taken out of the hands of the party and placed with new state machinery created by Gorbachev, especially the Presidential Council, which is answerable to him alone.

The whole process may be rapid or prolonged, but the Kremlin leadership’s plan was clear as soon as Foreign Minister Eduard A. Shevardnadze told the congress matter-of-factly that he didn’t think a governmental minister should sit on the Politburo as well.

Orthodox Marxist Yegor K. Ligachev complained that the government’s economic recovery plan was never discussed by the party’s top institution. In other words, the Politburo, an institution that dates back to Vladimir I. Lenin, is losing oversight over foreign policy and the economy, two of the most crucial areas for Gorbachev’s reforms.

Kremlinologists have commonly referred to the “ruling” Politburo, but the institution seems fated to become a second-class body. Now at 12 members and the domain of Moscow-based party barons and government leaders, the Politburo is to be flooded by the party chiefs of all 15 Soviet republics, plus a handful of nominees, perhaps six, from the Central Committee.

Under the new rules of Gorbachev-era politics, party chiefs from the republics will have a political stake in assiduously promoting the interests of their homelands, and in most cases will have had little or no experience in forging Soviet domestic or foreign policy. The Gorbachev brain trust, including Shevardnadze and Yakovlev, wants out of the Politburo, and those factors, plus the fact that the body will meet only once a month, instead of weekly as before, should make its influence shrink rapidly.

- The Central Committee, the party’s official policy-making body, will balloon in size to 398 members as a new formula is used to give each of the Soviet republics five members, plus an additional member for every 100,000 Communists. Another 85 seats will go to the higher echelons of the party apparat , government and Soviet Academy of Sciences.

Such quotas should maintain the dominance of ethnic Russians, but it is already obvious that there will be an eclipse in influence.