FOR 10 OR 20 years the great question has been building in South Korea of whether this rapidly developing, high-achieving country could have a political system as democratic as its social and economic system is mature. A substantial part of the answer is being revealed by this week's presidential election. The result matters not just to Korea but also to the United States, which takes pride in a friend's and ally's democratic passage and sees success as the best assurance of stability in a country and region where major American security interests lie.

These are the first direct national elections since 1971, when the army prevented the true winner, Kim Dae Jung, from taking office and installed an electoral procedure it could easily rig. This system of indirect elections endured until last summer. Huge national protests then induced the ruling party's candidate, a former general named Roh Tae Woo who assisted in the coup that brought outgoing president Chun Doo Hwan to power, to accept direct elections. Kim Dae Jung had promised to step down in favor of fellow oppositionist Kim Young Sam if the government made this stunning and unexpected concession to democracy. In the event, however, he broke his word, dividing the opposition vote and giving Mr. Roh an opportunity to win.

Before the vote, many Koreans were predicting that young people would take a Roh victory as evidence of fraud and go into the streets and that the armed forces would not accept a victory by their old nemesis, Kim Dae Jung. Kim Young Sam was portrayed as the moderate candidate acceptable to both students and generals and therefore best positioned to survive as a minority president and to coexist with a legislature likely not to be under his party's control.

Whatever now unfolds will be watched with great hope, and with great anxiety, by the United States. When the big demonstrations got under way in Korea last spring, the United States faced being depicted and dragged down as the patron of repressive military rule. Events and its own policy of catch-up spared Washington the worst of that fate. But such is Korea's dependence on American patronage, and its ambivalence about that dependence, that a considerable risk remains. The best response is encouragement of the Koreans' own efforts to make their fledgling democracy work.