Congressional manhandling of our foreign relations is nothing new. But in the past few weeks Mexico has become a prime target of willful legislative attack, with serious consequences for the national interest. On Tuesday Sen. Jesse Helms, chairing the Latin American subcommittee of the Foreign Relations Committee, told a packed hearing room that the 1982 election of the president of Mexico had been a fraud and hinted that the Mexican people should impeach him.

The chairman spoke for himself. He was cagey about certain statistics, which he claimed proved his case, except to say that they were "secret" and came from sources in the Mexican government. The rest of the subcommittee had never considered them. They also came as a surprise to the State Department and the intelligence agencies of the executive branch.

Mexico is in deep crisis. Oil prices have plummeted; inflation and unemployment are up. The government is in the final stages of sensitive negotiations with the International Monetary Fund on further adjustment measures that can only add to the sacrifices the Mexican people have borne so courageously since the beginning of the crisis in 1982. Brutal attacks from Washington on the central institutions of the nation are particularly gratuitous just now.

If the United States has one truly special relationship with another country in all the world, that country is Mexico. Standard diplomatic textbooks do not teach it. No other nation's internal developments impact so directly on us. With no other do we have such a range of concerns, from security to drugs, migration, border industries, energy trade and finance.

Nowhere else is there such a long border dividing -- but not separating -- a rich nation and a poor one. No other frontier in the world is marked by such stark contrasts of history, culture, language and living standards. And with no other country is the common relationship so asymmetrical.

It is said that the United States represents three-quarters of Mexico's foreign policy. When Washington speaks, the echoes are heard instantly in Mexico City. But for the United States, Mexico is a concern to which we turn only as an afterthought or in times of crisis.

Carlos Fuentes has said that for the United States it is "the most difficult frontier of all, the strangest, because it is the closest and therefore the one most often forgotten, most often ignored and most feared when it is stirred from its long lethargy." And so, he suggests, when we suddenly rediscover Mexico, there is a tendency to think we need to save it, to fashion it in our image, metaphorically to occupy it once again, to assimilate it to our own national experience, to make it something it is not.

This time around, Congress has become the base for what appears to Mexicans to be an organized attack. Mexico's economy is said to be in ruins. Its officials have been accused of complicity in the drug trade and of being guilty of rampant corruption. The very nation that for decades had been the toast of the hemisphere for its stability, its avoidance of coups and its distaste for military dictatorships is now alleged to be threatened by political dissolution.

Such rhetorical excesses do not serve the management of the delicate relationship. Noisy attacks on Mexico strike back at our own national interests. They are bound to increase nationalism, unite the factions of Mexican politics, inflame the always latent distrust of gringos and dissuade the leadership of the country from staking its political future on working with the colossus of the north.

The attacks on Mexico sit even less well because there is an element of self-righteousness about them. Mexicans know that their drug problem would not exist but for the insatiable market for drugs in the United States; they regard capital flight as a function of the fact that the U.S. financial markets are driven by our deficit to suck up the savings of others; they know that no nation, and certainly not the American South, has a perfect record of electoral honesty.

Solutions to the Mexican financial crisis, the drug crisis and the migration crisis can come only with growth in Mexico -- more production, more legitimate exports, more jobs. This, in turn, means bilateral development cooperation between the United States and Mexico, not unilateral confrontation.

A nation can choose its friends, but not its neighbors. We and Mexico are fated to live together. For richer or for poorer. No death can us part. We had best learn to exist side by side, with civility and understanding. What injures Mexico does damage to our own vital national interests as well.

The writer is a Washington lawyer and a former assistant secretary of state for Latin American affairs.