AT the ripe and enduring age of 62, Mexico's Institutional Revolutionary Party, known as the PRI, now holds the title of world's longest ruling political party. Until last week, there's been a qualifier: "in the noncommunist world."But it seems the Communist Party's over. The PRI, on the other hand, as it proved in congressional and gubernatorial elections two weeks ago, keeps rolling on. Mexico and the Soviet Union have little in common, except that they are both in transition. President Carlos Salinas de Gortari's reign has been accompanied by a resolute shift away from a statist, protectionist economy - reforms that have been dubbed "Salinastroika." Mikhail Gorbachev may have minted the term perestroika, or restructuring, but President Salinas, in terms of economic reform, is having far more success in implementing it. Subjecting a blubbery federal bureaucracy and subsidy-fed state corporations to the rigors of the marketplace, Salinas is cutting government debts. A North American free-trade agreement will further pry open the economy to international goods and competition. Inflation in the first half of this year is up a mere 9.1 percent - the lowest in 13 years. Even with an economy closely tied to the recession-slowed United States, Mexico's gross domestic product expanded at a 4.8 percent clip through June - the bi ggest rise over the same period in a decade. The unraveling of the Soviet Union has even raised hopes here that investors set to plunge their capital into Moscow or Eastern Europe may now find Mexico's stability more attractive. But what of glasnost, or political openness, in Mexico? The ballyhooed "democratic" reforms of the PRI have been an uneven affair. Opposition parties agree the new electoral laws and institutions are an improvement. But the PRI's sweeping victory in this month's elections - boosting the PRI's legislative leverage to a nearly two-thirds majority - are dogged by widespread complaints of continued vote rigging. Even if fraud were eliminated, the opposition parties say news media access and resources give the ruling PRI a big edge. Official claims that Pronasol, the government's anti-poverty, public-works program, was not used as a campaign tool seem disingenuous in light of recent budget figures. Pronasol spending in the month before the election rose 31 percent over prior months. In an apparent move to appease critics here and abroad, the PRI gubernatorial candidate in the state of Guanajuato renounced his victory last Thursday. This came after state authorities declared the PRI candidate the winner. "Legally [and] technically he was the winning candidate," says a senior government official. But a "consensus" decision - that the official says included Salinas - was made to hold new elections. Why? Because protests by the opposition were making Guanajuato "politically difficult to govern" and there were certain "irregularities" in the vote, the official says. While appearing magnanimous, the action also may appear authoritarian, if the central government is ignoring state laws and institutions to polish PRI's image. Political analyst Denise Dresser says reformer Salinas is out to prove that perestroika must precede glasnost. Based on Gorbachev's predicament, he may be right. But glasnost in Mexico means "loosening up as little as possible," Ms. Dresser says. "The PRI doesn't want to commit political suicide." And if Fidel Castro is looking for a new model, more acceptable in global circles, he may tear a page from Salinas' book rather than Gorbachev's.