President Lopez Portillo of Mexico made a deep impress as he presided over a spectacular economic boom and propelled his country into playing a prominent and independent role in international affairs. Mexico benefited greatly under his leadership. It will now be up to his successor, newly elected President Miguel de la Madrid Hurtado, to grapple with the severe problems which headlong economic growth has brought in its wake.
It is said that Mr. de la Madrid is more technocrat than politician, and this probably augurs well. The nation's ills - unrelenting population growth, widening gap between rich and poor, high unemployment, soaring inflation, slowed growth, huge foreign debt - seem to call for the kind of managerial training and experience which the new President has. They also call urgently for a ''moral renewal of society'' - the theme on which Mr. de la Madrid campaigned. If this proves to be more than political rhetoric, Mexicans should be able to look forward to a more just and equitable society.
Getting rid of institutionalized corruption will not be easy. But the President-elect vows a vigorous battle. He intends, for instance, to ask officials in his administration to submit a financial statement upon entering and upon leaving office. He has also made a point of having no stock in industry, a stance no doubt influenced by his first-hand observations of the way US government officials divest themselves of financial holdings. In any event, it is such an ethical posture, combined with sound belt-tightening economic policies, which can provide the needed impulse for Mexico's further progress.
The people of the United States, for their part, have more than a passing interest in what happens in Mexico. No relationship is more important today, as millions of Mexicans continue to stream illegally to the US for jobs and as US society takes on an increasingly Hispanic stamp. Mexican-US relations are reasonably good at the moment, thanks to the efforts of President Lopez Portillo and President Reagan. But the frictions caused by immigration, trade, and other issues have not disappeared and remain to be dealt with sensitively and understandingly. Having been educated partly in the US, Mr. de la Madrid has an appreciation of the US view which should make solutions easier to find.
As he begins his tenure, the new President should know that he has the good will of his neighbors to the north. Americans can be pleased not only that Mr. de la Madrid speaks their language but that he won decisively in an election which, despite charges of minor irregularities and despite the fact that Mexico has only one dominant political party, was more democratically run than in the past.