High abstention rate puzzles Mexico. How could most competitive election bring out so few? THE NUMBERS GAME

As official election returns give Mexico's ruling party candidate a two-to-one victory margin, political analysts are raising their eyebrows over an even more surprising statistic: More than 50 percent of 37.7 million registered voters did not cast a ballot last Wednesday. At first glance, it seems out of tune with an election that was considered the most competitive in modern Mexican history. In the rather mundane 1982 presidential vote, the official abstention rate was just 31 percent.

Six years later, political interest seemed to have been ignited by a continuing economic crisis and two dynamic candidates who opposed the likely winner Carlos Salinas de Gortari.

Just last week, government officials and opposition candidates alike were applauding the ``massive turnout'' at the polls. The Federal Election Commission even cited the crushing weight of high voter participation as one reason why official results were postponed for a week.

So what explains the high abstention rate?

Mexican political analysts say there is no contradiction: The problem is all previous statistics were warped by fraud.

In a subtle twist of logic, they say, this year's political ``awakening'' helped prevent the fraudulent manipulation of abstention numbers by the ruling Institutional Revolution Party (PRI) - and so contributed to an abstention count higher and more accurate than in other elections.

Over the years, the PRI has been accused of usurping the names of apathetic nonvoting Mexicans to inflate its own total, increase the aura of voter participation, and make its victories seem more sweeping.

``In 1982, the vote was inflated tremendously just so Miguel de la Madrid could surpass the results of [his predecessor J'ose] L'opez Portillo,'' says political scientist Ignazio Marv'an. Despite attracting a lower percentage of voters (71 percent) than any previous PRI candidate, President de la Madrid won with more votes (15 million).

``In a competitive election,'' Mr. Marv'an says, ``you can't manipulate the vote like that.''

And last week's election was surely competitive. Left-leaning candidate Cuauht'emoc C'ardenas, citing inside government information, claimed victory last weekend and called for a protest march this Saturday. Mr. C'ardenas, a former PRI governor and son of Mexico's most revered president, has undermined the PRI's traditional bases of support, pushing the old party share of the vote down by nearly 20 percentage points from its 1982 level.

Indeed, in just six years, the political landscape has dramatically changed from a virtual single party system to the shaky beginnings of multiparty competition. This year, both the right-wing National Action Party (PAN) and C'ardenas's National Democratic Front blanketed most of Mexico's 55,000 voting booths with volunteers who tried to prohibit the kind of fraud practiced by the PRI in previous elections.

Most government and PRI officials seem intent on addressing only the technical aspects of abstention, casting aside its often murky connection with fraud. The high abstention rate ``is surprising,'' says Amador Rodr'iguez Osando, a special government adviser to the electoral commission. ``The people have only woken up in the rural areas. The opposition parties don't have much of a presence in the countryside. And when there is no competition, people don't vote.''

But in private, some Salinas supporters say he has apparently warded off the temptation to pad his totals with abstention votes. ``To a certain degree, this reflects well on Salinas,'' a senior PRI official says. ``He didn't use abstentionism to inflate his vote. He didn't use the old machinery even though it was available.''

Another part of that old machinery, analysts say, is an artificially padded electoral register. Indeed, some say an inflated list, more than a low turnout, may account for the seemingly high level of abstention. This year, out of Mexico's 42 million eligible voters, a record 37.7 million reportedly registered, nearly 90 percent.

Opposition politicians estimate that the electoral register has been inflated by about 3 million voters (8 percent). In Sinaloa State, home of PAN candidate Manuel Clouthier, for example, PAN officials say names of deceased voters have recently appeared on the lists while many PAN supporters' names have disappeared.

Whatever the actual causes, the high abstention rate has reduced the narrow mandate that Salinas won with a claimed 53 percent of the vote.

In 1982, de la Madrid was the first president to be backed by less than 50 percent of the voting public. Salinas will likely take office Dec. 1 with the actual support of only a quarter of the eligible voters.