Mexico City — Mexico's economy may be feeling its worst quake since the 1930s, but the country's political structure appears to be shockproof.
''The system did for a time appear threatened,'' says a close adviser of President-elect Miguel de la Madrid Hurtado. ''There was even talk of its early demise. But it clearly has survived to live another day.
''To paraphrase that old adage on the king's death, 'The system is dead, long live the system.' ''
Mexico's governing party, the Partido Revolucionario Institucional (PRI), appears simply to have adapted to the crisis. Although there are factions within the party, they did not exploit the predicament, and as a result some say the party that has governed Mexico for more than 50 years may have grown even stronger.
The weathering of the economic crisis also illustrates the adaptability of Mexico's leaders.
Take President Jose Lopez Portillo. He came to office in 1976 from the right, but when he steps down Dec. 1, it will be on the left.
Mr. Lopez Portillo took over the presidency as an advocate of private enterprise. He fostered business expansion and was generally viewed a conservative. He staked out a position on the right wing of the PRI - counterbalancing his immediate predecessors, who were the darlings of the party's left wing.
Then near the end of his term - amid economic storm signals, including evidence that Mexico was almost bankrupt and unable to pay an $80 billion foreign debt - President Lopez Portillo reversed signals and moved leftward.
He nationalized Mexico's private banking system.
The takeover was a bold step aimed at resolving the near-bankruptcy of Mexico's leading banks. It was a move every bit as sweeping as President Lazaro Cardenas's nationalization of the oil industry in 1938.
It enfuriated the President's more conservative supporters but delighted the left wing of the PRI and assured Mr. Lopez Portillo a place among Mexico's leftist political heroes.
This political swing is not unusual; other presidents have swung dramatically from right to left or left to right during their six-year terms in office, confounding supporters and delighting enemies.
This reflects something of the way in which the Mexican political system functions and continually adapts itself. The PRI is perhaps the strongest, oldest, and most entrenched political institution in the third world.
It is less a political party in the traditional sense than a system of control that ensures its survival.
The PRI is a broad umbrella embracing the political spectrum from extreme left to extreme right; it represents business and labor, city and countryside, the young and the old, the professions and the students, the educated and the uneducated in a much more effective way than political parties elsewhere.
It has even developed a talent for capturing former opponents - either through cooption or coercion. Many of Mexico's small leftist parties, for example, are reportedly on the PRI's dole.
But because the PRI embraces such a wide sprectrum of Mexican life, new government policies benefiting one group or another within the system inevitably damage the interests of others - and so the PRI is continually trying to balance itself between those interests.
''The PRI giveth and the PRI taketh away,'' comments a long-time observer of the system, ''and that's how it stays in business.''
Still, some observers have begun to wonder if the system might not be unraveling. After 50 years, the PRI was seen as having outlived its usefulness. It appeared less responsive to the needs of Mexicans, especially those in the middle class.
Many openly asked if it was not time for a new system.
Armando Ayala Anguiano, editor of the monthly Contenido, indicated as much in his latest, critically acclaimed book, ''Mexico in Crisis: The End of the System.''
Issued last August, the book argues that it is unlikely President-elect de la Madrid will be able to deliver on his campaign promises because of the enormity of the problems facing Mexico, and that the system would therefore likely fall apart. At the time there was widespread acceptance of such views.
Now, however, these views appear dated. To be sure, Mr. de la Madrid is not yet in office, but the system has weathered an extreme storm and emerged intact.
Mr. Ayala now says: ''I see less of a chance of a split in the PRI . . . than I did before the (bank) nationalization.''
A close adviser of Mr. de la Madrid says: ''The economic crisis forced the decision to nationalize the banks and in the process united the party. The PRI actually was strengthened by the crisis.''
That view is echoed over and over again in the press and in opinion circles from left to right.
Adolfo Aguilar Zinser, a political scientist with a leftist think tank, puts it forcefully: ''The President (Lopez Portillo) has strengthened the PRI and those of its segments favoring redistribution of wealth.''
Moreover, the move fits the pattern of government rhetoric here that is constantly touting a leftist-populist line in honor of the Mexican Revolution of 1910. That revolution is always referred to with a capital ''R'' and is seen as ongoing.
During his presidential campaign late last year and through the election July 4, Mr. de la Madrid repeatedly hawked the theme of revolution and its continuing role in Mexican life.
As Mr. de la Madrid looks to his presidency, scheduled to begin Dec. 1, he can certainly be discouraged by Mexico's ravaging inflation, unemployment, the flight of dollars from the country, Mexico's near-bankruptcy, and its huge foreign debt.
But his political task may well have been made easier by the bank nationalization.
Ironically, he apparently was not strongly in favor of the move. In fact, his advisers say he was informed of the nationalization just hours before Lopez Portillo announced it Sept. 1. They say the President-elect was not consulted. Subsequently, he publicly endorsed the move - but his words were tepid enough to make plain he did not think it was such a good idea.
Yet he may look back on it as a purposeful step that made it possible for him to get on with the task of setting the Mexican economy on its feet without having to face a deteriorating political system.