In the good old days, when everything naturally was better, American politics was supposed to stop "at the water's edge." It seldom did, of course. The history of this century is replete with examples of how extreme partisanship -- the U.S. politician's penchant for exploiting narrow, emotional issues for personal or party gain -- worked against the nation's long-term interests.

These included:Senate rejection of the League of Nations treaty, wrecking President Woodrow Wilson's post-World War I dream of an effective international organization to ensure world peace.

Fanning of isolationist sentiments, keeping America from becoming militarily strong and nearly leading to defeat of the Selective Service Act after World War II had begun.

Politically inspired scapegoating about "who lost China" after that war.

Witch hunts of the McCarthy era that paralyzed America, scarring its politics and policymakers for years.

Thus, it is no surprise that the air here these days is filled with predictably partisan political rhetoric as the first visit of a Soviet leader in 14 years approaches.

House Republicans, to their discredit, threaten to walk out if Mikhail Gorbachev is granted the same privilege allowed such dictators as Ferdinand Marcos: addressing Congress. That action virtually guarantees that President Reagan would be denied a similar opportunity to address the Soviets on his expected visit to Moscow next year. It also runs counter to the most fundamental notions of free and open exchange of opinions in a democracy.

Reagan, who deserves bipartisan praise for seeking a practical reduction of the arms race by negotiating with the Soviets, has felt compelled enough by right-wing Republican criticism of the proposed arms treaty to have injected harsh Cold War invective days before Gorbachev's arrival.

In a Florida political speech, he offered Gorbachev the kind of gratuitous advice that would infuriate American politicians if it came from a Soviet official. The Soviets should "make their country like ours -- a place that people don't want to leave," Reagan said. He followed that up by putting out the word, through his spokesman, that the talks with Gorbachev should not be regarded as a meeting between "old friends" but as "a summit between old enemies."

Such political posturing need not detract from the very important business at hand -- seizing yet another opportunity to reduce the destructive impact of Cold War politics on life here and everywhere.

Now, as in the past, the issue is not whether America surrenders its principles by dealing with communists. It is a question of self-interest. For two generations, the Cold War has diverted massive amounts of U.S. energy and resources from what former senator J. William Fulbright (D-Ark.) called "the creative pursuits of civilized society to the conduct of a costly and interminable struggle for world power."

U.S.-Soviet competition also produced constructive results. As Fulbright noted, in a masterful speech 23 years ago:

"Directly or indirectly, the world struggle with communism has stimulated economic and industrial expansion, accelerated the pace of intellectual inquiry and scientific discovery, broken the shell of American isolation and greatly increased public knowledge and awareness of the world outside the United States. At the same time, the continuing world conflict has cast a shadow on tone of American life by introducing a strain of apprehension and tension into a national style which has traditionally been one of buoyant optimism . . . .

"Overriding all these changes, however, good or bad, has been the massive diversion of wealth and talent from individual and community life to the increasingly complex and costly effort to maintain a minimum level of national security in a world in which no nation can be immune from the threat of sudden catastrophe. We have had to turn away from our hopes in order to concentrate on our fears, and the result has been accumulating neglect of those things which bring happiness and beauty and fulfillment into our lives."

One doesn't have to dream that the Reagan-Gorbachev talks will lead to a world of happiness and beauty. Considering the superpower realities of the late 20th century, too much is at stake to permit partisanship to wreck next week's chance at establishing a more stable, secure world. The sum of this summit is far greater than any of its petty political parts.