Mexico's ruling party won a key governor's race Sunday in a state election that analysts say offers an important reading of voter attitudes a year before the country's next presidential contest.

The victory in the state of Mexico should give a psychological boost to the ruling Institutional Revolutionary Party, known by its Spanish initials PRI, after lackluster performances in other recent campaigns. And the results will undoubtedly prompt soul-searching by the two main opposition parties as they select candidates and strategies for the July 2000 presidential election.

With 93 percent of the ballots counted, the PRI's Arturo Montiel Rojas had captured an insurmountable 41 percent of the vote. Jose Luis Duran Reveles of the center-right National Action Party had 34 percent and Higinio Martinez Miranda of the center-left Democratic Revolutionary Party had 21 percent.

At the same time, in another governor's race in the Pacific coast state of Nayarit, the PRI was soundly defeated by a coalition of four opposition parties that included the two major opposition parties. With 86 percent of the vote tallied, coalition candidate Antonio Echevarria Dominguez had 52 percent compared to 43 percent for the PRI's Jose Lucas Vallarta Robles.

The election in the state of Mexico was considered significant because the jurisdiction, which is roughly the size of New Jersey and surrounds Mexico City on three sides, mirrors the country at large. It is Mexico's most populous state with 12.7 million people and it accounts for more than 10 percent of the country's gross national product. The state also reflects Mexico's demographic diversity, with pockets of indigenous people, swaths of agricultural land, large middle-class suburbs and urban slums.

The state's 7.3 million registered voters represent almost 13 percent of Mexico's total electorate. About 47 percent cast ballots.

If their collective judgment was good news for the PRI, it was bad for the leftist Democratic Revolutionary Party and its likely presidential candidate, Mexico City Mayor Cuauhtemoc Cardenas. Because of its close ties to the capital, many observers saw the state of Mexico vote as a partial referendum on Cardenas's performance since he became the first elected mayor of Mexico City two years ago. During his term, the city has been plagued by crime, corruption and a declining economy--problems Cardenas inherited but has been unable to solve.

"This is a real kick in the derriere for Cardenas because he was a clear liability" for his party's state of Mexico candidate, said George W. Grayson, an expert on Mexican politics at Virginia's College of William & Mary who monitored the elections here.

At the same time, the Nayarit results seem to confirm the conventional wisdom that the PRI can be defeated when opposition parties unite and do not split the vote. That will likely lead to renewed calls for a coalition presidential candidate next year, a compromise that seems unlikely. Even so, the fact that the PRI's relatively weak candidate in Nayarit got 43 percent of the vote against such a broad coalition indicates that the opposition parties have their work cut out for them.

CAPTION: Eventual winner Arturo Montiel Rojas of Mexico'sruling party enjoys earlyreturns in governor's race.