EL SALVADOR is Nicaragua with a difference. Like Nicaragua, it was for decades dominated and exploited by a small corrupt elite. But El Salvador's elite was toppled, just two weeks ago, at a relatively earlier stage in the country's deterioration by a coup that preempted what otherwise would doubtless have been a longer, more destructive, more polarizing armed struggle that would have left all power with the military victors, as in Nicaragua. The result is that some kind of moderate solution may still be possible in poor, small El Salvador, where a joint civilian-military junta now tenuously rules.

To be sure, this is not guaranteed. The formal political structure in this Central American "domino" had largely yielded to the reality of anarchy and violence. But the fall of the Somoza regime in neighboring Nicaragua, where Salvadorean leftist helped (and practiced), came at a "good" time. It not only emboldened the Salvadorean challengers and demoralized the oligarchy, which was, one must emphasize, totally discredited already. It also spurred the United States into a burst of preemptive diplomacy in which it made clear to all sides its conviction that change must come as quickly and peaceably as possible.

The United States did not sponsor the coup; at least no one has seriously claimed so. But it did shake off the self-shackling fear of being charged with "intervention" that had so long immobilized American policy, and allowed violence to escalate, in Nicaragua. Thereby it was able to identify itself to some extent with the elements that were forcing change anyway in El Salvador.

Since the coup, however, the administration seems to have lost its nerve. Though the new junta has said the right things about reforms, rights and elections, it is uncertain and weak, and it has not been able to assert its authority over either the unreconciled right or the impatient left, both of which are armed to the teeth. The United States has offered good wishes but, so far, not the specific assurances of aid that the junta needs to start delivering on its promises to the people and to show that it can make its way in the world. The junta evidently could use some tear gas, a legitimate tool for controlling and curtailing street distrubances, yet the State Department has been slow to consider licensing commercial sales of the stuff on grounds that the new government in San Salvador has not proven its worth. This is the way to maintain purity of policy -- and to turn El Salvador back to a brutal Nicarguan-type civil war.