What did President Reagan expect to find this past weekend as he made his first visit to Mexico since before his inauguration? In a recent State Department forum, former national security adviser Zbigniew Brzezinski warned that Mexico could become the next Iran. Sen. Henry Jackson has also raised the specter of upheaval below the Rio Grande.
A confluence of indicators support these Cassandra-like predictions. A staggering $83 billion foreign debt, huge budget deficits, a 100 percent inflation rate in 1982, and a sharp fall in oil prices have forced upon Mexico a stringent austerity program, fashioned by the International Monetary Fund.
Such belt-tightening comes at a time when open and disguised unemployment afflict over half the able-bodied work force in this cornucopia-shaped nation of 73 million inhabitants. Prices continue to soar, the Central Bank is starved for hard currency, factories operate at 43 percent of capacity, and a protracted drought has devastated production in the countryside where the majority of campesinos live in hard-scrabble poverty at the base of an increasingly squat social pyramid.
Last month, in separate incidents in Mexico City and in Guerrero state on the Pacific coast, strikes and sit-ins led to clashes with police that left several hundred men and women injured, some seriously.
Revelations of corruption during the 1976-82 presidential sexennium have intensified cynicism in a country where rateros (thieves), ladrones (robbers), and banditos (bandits) are street synonyms for politicians. The former director of the National Pawnshop, a quasi-public agency, stands accused of stealing more than $13.5 million. The attorney general has charged Sen. Jorge Diaz Serrano, ex-head of PEMEX, the state oil monopoly, with defrauding the government of $34 million in connection with the purchase of two natural gas tankers. These sums are small potatoes compared to the $10 billion worth of oil that allegedly disappeared from PEMEX under the last administration.
The worst economic conditions since the 1910 revolution, and deep-seated alienation notwithstanding, a medley of factors militate against Mexico's going the way of Cuba, Nicaragua, and Grenada.
* President Miguel de la Madrid, inaugurated last Dec. 1, has inspired confidence by recruiting a skilled team of financial and administrative experts whose straight-talk and economic performance have won high marks from the IMF.
* Mexican leaders are adept at manipulating symbolic appeals to divert attention from pocketbook issues. A vigorous and popular anticorruption campaign keyed on Diaz Serrano, a so-called ''big fish'' of corruption, appears as the latest version of this tactic, called ''moral renovation'' by the Harvard-trained chief executive.
* Fidel Velazquez, who rules Mexico's dominant labor confederation (CTM) with an iron hand, has coupled militant advocacy of higher wages with a readiness to accept modest pay increases compatible with the retrenchment plan.
* The ruling Institutional Revolutionary Party, though overly centralized, heavy-handed, and filled with hacks, has slowly begun to modernize - with an emphasis on selecting able candidates in the 1,158 municipal elections scheduled for this year. Party president Adolfo Lugo Verduzco, Interior Minister Manuel Bartlett Diaz, and Education Minister Jesus Reyes Heroles are astute champions of cautious reform.
* Political cannibalism besets the left where parties sprout like mushrooms in a dank cave. Hardliners will soon challenge Eurocommunists for leadership of the Unified Socialist Party of Mexico (PSUM), a left-wing amalgam that captured 4.3 percent of the votes in last year's congressional contests. Knowledge that the army, which massacred hundreds of rebellious students in 1968, will brook no guerrilla shenanigans has thus far kept extremists in PSUM, the Trotskyite PRT, and the Castro-oriented Corriente Socialista from trading ballots for bullets.
* The well-to-do middle class, the greatest relative loser in the economic crisis because of inflation and the inaccessibility of dollars, will continue to grouse, while moving into smaller condominiums, evading the new tax on cars, and voting for the business-focused, pro-Catholic National Action Party for which unity and revolution are anathemas.
* The 125,000-man armed forces, though hardly Prussian, have begun to shape up with armored vehicles replacing horses in cavalry units, the introduction of German-designed G-3 automatic rifles in the 71 infantry regiments, and the acquisition of a dozen F-5 supersonic aircraft. Military leaders continuously trumpet their loyalty to the political system.
* Extended families, in which a couple of members work fulltime and others hawk lottery tickets or shine shoes, provide a safety net for millions of people in a country where social security coverage is limited and unemployment compensation nonexistent. The most attractive welfare scheme is a porous US border through which a record number of illegal migrants passed last month.
* The United States, whose vital interests are linked to its neighbor's stability, has provided advanced payments for oil purchases, export credits, and commodity guarantees - including $1.7 billion for grains - to prevent bankruptcy and starvation here. Self-interest assures future assistance if conditions deteriorate in this ancient Aztec nation.
Agitation, demonstrations, and strikes will mount as economic conditions continue to worsen for another two years or so. But absent a catastrophic event - the collapse of world oil prices or runaway inflation, for example - Mexico should avoid revolution.
The lack of a charismatic opposition leader (or any strong opposition leader, for that matter), a national network of organizers, or a compelling ideology around which to rally support distinguishes Mexico from Iran and makes comparisons between the two countries naive if not misleading.