The cold front moving across the country from conservative quarters is in the nature of a sigh of relief that somehow Ronald Reagan didn't go to Geneva and sell the store. It is a curious vote of confidence. It is also an interesting commentary of a popular view about the value of summitry.

What the president's best-friends- turned-critics are saying is that the only thing preferable to the summit would have been to have had no summit at all. Their reasons range from the implication of "moral equivalence" conveyed by the respect Reagan and Gorbachev paid each other to the unbridgeable ideological gulf between our two systems and the innate treachery of the Other Side. Their conclusion: an exchange of the Bolshoi for the Beach Boys is about as far as U.S.-Soviet relations should be allowed to go.

The proof of this proposition is supposed to be the emptiness of the U.S.- Soviet summit encounters in the postwar era. It is an easy argument to make: a succession of summit exercises conducted by Eisenhower, Kennedy, Nixon, Johnson, Ford and Carter did not resolve the Cold War; they did not forestall the crisis in Hungary, the Berlin Wall, the missiles in Cuba, the assault on Czechoslovakia, communist encroachments in Ethiopia, Yemen, Afghanistan, Angola, Nicaragua and Cambodia; the shoot- down of KAL 007. They did not put an end to Soviet espionage, or gross violations of human rights in the Soviet Union.

So much for the idea of the leaders of the two superpowers getting together. "The sheer nothingness of the (Geneva) conference is its paramount achievement," William F. Buckley Jr. argued recently. The soaring thought in the aftermath of Geneva is that this kind of talk is coing from what is thought to be an ascendant body of opinion in American politics -- a conservative renaissance.

But there is also a consoling thought: the political leader of this renaissance, Ronald Reagan, gives every evidence of having moved into the camp of those who do not just talk about it but are obliged to come to grips with the reality of managing relations with a powerful adversary and anxious allies while responding to the tugs and hauls of domestic politics at home. He has joined the rest of the postwar presidents who accepted summitry as a necessity of life in the nuclear age.

If you take into account the alternatives that history does not disclose, the awful things that have happened in spite of postwar summitry are not necessarily the whole story. Ponder how much worse things might have been if the leaders of the United States and the Soviet Union had coolly kept their distance.

That is the tormenting dilemma of preventive diplomacy. There is no way to demonstrate the consequences averted by trying to diffuse confrontation; to define what is intolerable behavior by both sides; to reach even modest treaty agreements. There is no handy measure of good things derived or bad things avoided by having the two top men take each other's measure and hear each other's case. But that is no reason to abandon preventive diplomacy.

Leaving aside what each man may think he gained in the Geneva meeting, the meeting justified itself with one accomplishment: the agreement to meet again, not once but twice. There is something to be said for making these encounters commonplace.

This is what British Prime Minister Harold Macmillan had in mind 25 years ago when he deplored the crisis-creating, propagandistic quality of one-time summit meetings and argued for a "chain of peaks." To a lot of people, it sounded too sensible and too orderly for a disorderly East-West relationship. Yet we are closer to the concept of regularity in summitry as a way of easing the confrontation than we have ever been.

That opportunity would not be presenting itself if the head-knocking at the most recent summit meeting had not been vigorous enough to test just how far either side was ready to go. The brinkmanship demonstrated that when push came to shove, there was a recognition on both sides that while some of their differences were profound and irreconcilable, some were not -- and that there were good reasons to address those that might be reconcilable.

Not the least of the reasons was an apparent mutual recognition that this was not just a debate between two great powers over clashing concerns and opposite ideologies; that others had a stake in the handling of the superpower conflict; and that how well or badly it was handled by the superpowers would directly affect their standing and their interests in the rest of the world. Insofar as Ronald Reagan and Mikhail Gorbachev came to those conclusions at Geneva, the world is markedly better off.