For the Soviet Union, the Olympic Games are a matter of legitimacy, and that makes them a matter of grave concern. Participants in the debate over whether to boycott the Games in Moscow this year to protest the invasion of Afghanistan should realize that no other non-military move could so directly challenge the Soviet leadership, or so startle the Soviet public.

The quest for legitimacy has been one of the principal themes of Soviet history since the Bolshevik Revolution. This is not surprising in a system controlled by revolutionary usurpers. No Soviet leader has ever won a legitimate election, nor even inherited legitimate sovereign power.This simple fact guarantees the insecurity of Soviet leaders -- insecurity that leads, for example, to the harsh repression of Soviet dissidents even as they are dismissed in official accounts as a meaningless fringe element. Dissidents of any kind must terrify insecure autocrats.

The contemporary generation of Soviet leaders has sought to enhance its claim on the loyalty of 260 million citizens by increasing Soviet stature in the world and maintaining peace and prosperity at home. In Soviet terms, it has succeeded quite well on both counts. These have been good years for the Soviet autocrats.

But the fear of illegitimacy haunts the Soviet leaders still, partly because they know their society contains many potentially restless elements and partly because the Soviets have never been able to establish reliable, stable relationships with foreign countries -- even countries that they occupy militarily, like Czechoslovakia.

For many years the Russians sought to host an Olympiad, and repeated rejections of their applications caused anger and resentment. Finally, at a time when the era of detente seemed firmly established and when no other major country wanted to compete for the honor, the International Olympic Committee picked Moscow as the venue for this year's summer Olympics.

There should be no underestimating the significance the Soviets themselves put on their selection. They have been treating this Olympiad as one of the great events of their modern history, and the preparations have been lavish. The entire budget for new construction in the Soviet capital for several years has been devoted to building Olympic facilities. At the same time, the authorities have been making preparations to deport potential troublemakers -- including political and religious dissidents -- from Moscow during the Olympics. And until now, at least, they have refused to make arrangements to sell Western publications in Moscow during the Games.

Like Hitler in 1936 (and participants in this debate should also study that Olympiad), the Soviets are preparing a great propaganda offensive for this summer. Olympic committees in the West may see a distinction between politics and sports, but the Soviets do not, and never have. Only in the Soviet bloc do the same athletes represent their country in both professional and amateur world championships.

An effective boycott of the Games this summer would be a tremendous blow to Soviet prestige; but perhaps more significant, the collapse of this Olympiad would send a genuine shock through Soviet society. The leaders would explain it as a hostile manifestation of imperialism and, in the short run, might fan Russian xenophobia on their own behalf; but in the longer term, the failure of these Olympics could cause the first serious challenge to the legitimacy of Soviet power in many years.

The Soviet public today is not totally isolated from the outside. Tens of millions of Russians listen daily to foreign radio broadcasts; thousands more travel abroad or meet visiting foreigners. The idea that an Olympiad could collapse because of international disapproval of actions by the Soviet government would certainly sink in. The consequences of this are unpredictable, but they must terrify Soviet leaders.It might turn out that the Soviet people decide they have been humiliated by their own rulers. This is not necessarily likely, but it is possible.

A boycott of the Olympics will not retrieve the national sovereignty of Afghanistan nor ensure the future tranquillity of Pakistan and Iran, nor preserve Western interests in South Asia. But it would be a genuine punishment to the Soviet regime.

Moreover, a successful Olympiad would persuade the Soviet leadership that it has little to fear from the outside world, no matter what it has done to Afghanistan and the norms of international behavior. (Hitler reoccupied the Rhineland a few months before the 1936 Olympics.) Western Olympic committees may declare that by going to Moscow they are not endorsing the Soviet regime or its behavior, but the Russians will surely see it differently.