FOREVER, IT sometimes seems, the Olympics have been an arena not so much for athletic competition as for political vengeance. This year it may be different. Politics has not vanished from the Olympic scene, but for once political considerations are working to good effect: to bring nations in rather than to drive them out, and in that way to make the games true to their universalist sportsman's ideal. Specifically, the Russians are coming to the summer games in South Korea, despite the strong possibility that their ally in North Korea will choose not to. The Chinese, another ally of the north, are also expected to take part.

Confirmation of broad Communist participation in the Seoul games does more than ensure terrific athletic competition -- and terrific television. It also increases the chances that the odd men out in North Korea will not mess up the Olympics by threats or acts of terrorism. If they do engage in disruption, they will have Moscow and Beijing to answer to. The North Koreans, practiced killers who have only lately begun to abandon a hermit's pose, are obviously shaken to find themselves isolated internationally and conspicuously abandoned by their key patrons. But they have left themselves a sliver of maneuvering room on the twin issues of sending their own athletes to compete and hosting some Olympic events on their territory. Presumably Moscow and Beijing are speaking quietly to Pyongyang about the benefits of going with the world flow.

For South Korea, the latest word from Moscow is welcome support for its grand strategic hope to outflank North Korea, to narrow the Communist regime's options for violence and to compel it to explore an open and peaceful relationship on Seoul's terms. This is a transcendent time in the life of a country that was born as half a nation after World War II, taken quite accidentally under the United States' wing and, a few years later, invaded and devastated by North Korea and saved by its own and American arms.

Living all the while under a deadly security threat from the north, South Korea has since become not a perfect development model but a striking economic success story. Though its political travails may not be at an end, it can be said to have taken some long and difficult steps along a democratic path. The award of the summer Olympics to Seoul was received everywhere as international recognition of South Korea's national ascent. It is working to deserve the honor in full.