ONE UNDERSTANDS now why the guerrillas were so eager to destroy, and the political opposition to denounce, the elections in El Salvador. They seem to have sensed that the people would choose to take the way offered by the government to express their pent-up longing to have done with the war and to reconstruct the country.

That longing exploded on Sunday. Perhaps a million people voted, a total far surpassing the government's rosiest expectations and one considerably dissipating any suggestion that too few people would turn out to make the outcome reasonably representative. The process seemed fair. The voters came out despite death threats, logistical and procedural obstacles and a history giving little comfort to the notion that elections matter. They were repudiating the violent way represented by the guerrillas as by the death squads and associated soldiers. It was a tremendous victory for the political process.

That process now gets serious. President Jos,e Napoleon Duarte's centrist Christian Democratic party won a strong plurality. That means a coalition will have to be hammered out by some combination of the Christian Democrats and the other parties, none sharing fully the PCD's commitment to its reforms. The government that emerges will not be able to ignore the veto power of the armed forces. It will be, nonetheless, a government owing its first loyalty to the people.

On the eve of the elections, signs began to appear in San Salvador of the readiness of important Christian Democrats to negotiate with leftist insurgents to end the war. This may be an early challenge. The insurgents were hurt badly by the elections: they failed to intimidate or dissuade the masses and were substantially spurned by them--a result that we hope will not be lost on Mexico, France and the Socialist International, which have uncritically boosted the guerrilla cause. But the guerrillas, thanks in part to Nicaragua and Cuba, retain a formidable military punch. This strengthens the pressure on the new Salvadoran government--a government that may have some very unforgiving influences in it--to complete the isolation of the left by making a fair and generous opening to its democratic component.

The United States gambled on the elections, and won. Now it must maintain adequate support, keep pressing the reform line and stay out of the way of any Salvadoran efforts to arrange a local accommodation. The elections do not solve the American problem in El Salvador. Conceivably they may do something better: help enable the Salvadorans to work more effectively on their own.