PEOPLE WHO BELIEVE as we do that the contra force is not a useful instrument to bring to bear against the Sandinista government are obligated to answer a question: why would the Sandinistas, if they were relieved of the pressure of the contras, behave any better in the various ways that are crucial to Nicaragua's fellow Latins and the United States? Without the military pressure, would they have any incentive to negotiate or change?

There are three principal areas of concern, and two of them do not depend on contra help. First is the Soviet strategic threat. It is not and never was up to the contras to keep the Soviets from making of a communist Nicaragua a strategic base threatening the United States. That is our business, and repelling it is our responsibility. Either we protect our own strategic interests on the basis of a cold- eyed geopolitical appraisal or we don't. President Reagan should express his concern and his intention clearly and specifically to the Russians on this score. No missiles, no MiGs, no submarines and so forth -- and we will take direct action to keep them out. Other Americans should understand this well.

Second is the matter of protecting Nicaragua's neighbors from Sandinista subversion. It is something to which the contras can contribute only indirectly, and the United States must contribute a great deal in aid to development, defense and political institution-building, as it has been doing in El Salvador. The job is expensive, and it is worth it.

The toughest part is turning Nicaragua back toward democracy. For if the United States lets down the contras, the Sandinistas will be sorely tempted to crush the vestiges of pluralism in Managua.

We think, nonetheless, that the contras' folding would allow -- would compel -- the Latin democracies to demand reasonable conduct by a regional standard. The Sandinistas could no longer seek to justify militarization and domestic repression on grounds of external Yankee menace. The carrot -- for a country that seems unlikely to go on a permanent Soviet dole -- would be access to desperately needed economic support from European treasuries and Western banks. The stick would be the Latins' capacity to isolate Nicaragua economically and politically on a collective basis. The Latins also have it within their power to police borders, monitor the flow of foreign arms and advisers, and otherwise perform necessary security missions. American diplomacy would have the task of stiffening the Latins in this regard.

We do not claim this approach is sure to turn back the clock seven years to the ouster of the Somoza dictatorship. The realistic choice Americans face, however, is between two difficult sets of odds. We think support of an uncertain and Somoza-tainted military intervention has less chance of containing the Sandinistas' aggressive thrust than a policy that puts the burden of conducting a negotiation on Nicaragua's fellow Latins. It is the difference between taking a chance alone and following a course that puts the primary responsibility on friendly countries, which, for all their maddening weaknesses, at least know they must bear the principal consequences of their own default.