CHILLING police rush to "protect" a returning opposition figure brought the government of South Korea deservedly harsh condemnation just last weekend. On Tuesday, however, an election was held that produced a rather contrary reaction. The party of Kim Dae Jung, the returning exile, ran directly against the "military dictatorship" of Chun Doo Hwan and took 50 seats. The result is being read as a favorable comment on President Chun's loosening of the political process in the last year.

Did some of us perhaps give too much importance to the well-publicized drama of Kim Dae Jung's return? The image of him as a banned and abused politician seems not to square with the reality of the leeway offered his party in the campaign and with its success at the polls. But there is a reasonable explanation for it.

President Chun has the police on tap. He wanted to demonstrate his control of the turf when Mr. Kim returned, and he did, in a heavy-handed way. It remains, however, that President Chun, partly in response to American "quiet diplomacy," has been opening up the system somewhat: releasing prisoners, readmitting banned people to academic and political life. President Chun fit Mr. Kim into this pattern, letting him back in time to resume a shadow political role and to give his party a homestretch boost -- a kind of advertisement for President Chun too. So there is no contradiction between the rough stuff at the airport and an electoral process giving the opposition wider play: both reflect political decisions of Mr. Chun.

And both leave Mr. Chun firmly in control. This is the point. The military dominates politics, justifying it by the evident aggressiveness of communist North Korea. Mr. Chun, a retired general, represents the military class. Moreover, Korea's is a presidential system: the national assembly has no real power and the constitution gives the president's party a lock on it. The opposition will have more of a forum now. This could produce street and student actions of a sort that have traditionally led Korean presidents to show muscle. Still, the opposition has no ready way to reach power.

How is change to come about in a place like South Korea, with an increasingly middle-class society eager for democracy and an ambitious officer class bent on power? Internal forces will supply most of the answer. As South Korea's defender, patron and well-wisher, however, Washington cannot stop pressing for change. It must do all it can to guide the Koreans institutionally and to school them against abuses of police power. Otherwise, the cause of democracy is undermined there, and support for Korea is undermined here.

Something else is undermined, too. If the American government does not work effectively for freedom in friendly states, it diminishes its claim to be truly interested in working for freedom in unfriendly states. Korea tests American good faith.