ARGENTINE POLITICS throughout this century has repeatedly been seized by a perverse and self-destructive impulse that has done the country immense harm. One of the bearers of that tradition is the Peronist movement, and unfortunately, the Peronists are the chief winners in Sunday's election. They have taken most of the provincial governorships, and although President Raul Alfonsin's party continues to have more seats than any other in the national Chamber of Deputies, it no longer has the two-seat absolute majority that it commanded for the past two years.

It's not the pure arithmetic of seats lost that will undercut Mr. Alfonsin so much as the sense that his country is swinging away from rational and skillful leadership toward the darker and more adventurous alternatives that have always meant trouble for Argentina.

Argentina's huge debts to foreign banks were generated largely by capital flight. The government borrowed desperately to keep its currency from collapsing in the years under the military juntas when wealthy Argentines were sending their money by the tens of billions of dollars to New York and London. The best and easiest way for Argentina to repay its debts and stabilize its economy is to attract that money back home. The chances of that are going to fall at the same rate at which the Peronists' fortunes rise. In Brazil a weak government, trying to avoid the necessity for extensive economic reform, is now hunting for allies to join its moratorium on repaying foreign debts. If the Argentine government is immobilized and prevented from carrying out its own program of reforms now getting under way, the pressure on it to join a moratorium will rise. That's a shortcut to economic isolation and stagnation.

At the turn of the century, Argentina was one of the world's richest countries. Its GNP per capita was equal to that of the United States. It is now about one-sixth the United States' -- a rare case of a country sliding rapidly backward down the scale of economic development. What happened? It was the result of misguided politics -- the familiar mixture of fervid populism and nationalism represented in that big Peronist vote last weekend.