Let us inspect the reasons why the Reagan administration finds no merit in proposals, like one made here last week, for a new diplomatic path in El Salvador.

1) Policy-makers simply do not believe that the situation is deteriorating so badly that a new policy is essential. They see a military stalemate that at the least can be kept from getting worse, and they see an official Salvadoran political scene that may be shaking down after some heavy turbulence.

2) The administration believes it already has a decent and workable plan to end the war by a political route: to move toward the presidential elections scheduled in March 1984, drawing into the process some of the key civilian liberals who are now in the opposition and thereby dealing it a crushing blow. The administration is open to the thought of a negotiation between government and guerrillas, and it hopes the Mexicans and others in Latin America can help out, but it fears that a premature move to the table could bring the Salvadoran government down.

3) The United States cannot support any negotiation that has the effect of letting the left shoot its way into a greater share of power than the estimated 15 percent it might have gotten had it taken part in the constituent assembly elections last March. It would be dangerous, furthermore, to nourish the idea that the United States is good for only two or three years' worth of support in a nasty guerrilla war; staying power means at least four or five years.

4) Any plan to deal with El Salvador must take into account the life-sustaining support the insurrection receives from Nicaragua. Pressures the United States and others are putting on Nicaragua make it possible to ask if the Sandinista regime may now be ready to reconsider its support for the Salvadoran guerrillas.

These are not flighty considerations. But they are not conclusive either. There are answers to them: 1) The situation on the ground may be worse than the administration calculates. 2) The current American plan is awfully iffy. 3) Guerrilla influence can only grow as the war continues. 4) Why not talk more seriously with Managua?

The relevant question is not whether any single new proposal is fault-free but whether it may have advantages over the policy being pursued by the administration.

In El Salvador, we are "engaged in a partnership for peace, prosperity and democracy," as the president put it in his State of the Union address. That is, we are helping our friends slug it out.

This is a principled course--though not all the principle is on one side. It may also be a blind alley. The operation--our support of the government--may be succeeding or at least not failing. But the patient--the country as a whole--may be on the way to dying. We have seen it happen before.

To rescue El Salvador and to recoup as much as possible of the large American political investment in the country, there is a need, I think, for the sort of diplomatic initiative to which the president pointed with pride, in respect to other regions and other issues, Tuesday night.

The United States might well consider following its own Mideast example by accepting the urgency of the Salvadoran situation and offering a plan meant to appeal to the non-extremists on both sides.

Under such a plan there would be a cease-fire and the two sides would be left to work out their own political future, which would no doubt be ragged and irregular. The Salvadoran government would lose the support it now gets from the United States for its plan to parcel out power by its own elections; in return, it would gain a cease-fire. The opposition would lose the edge that accrues to it by its military pressure but would get an earned or agreed place in the political sun.

This is the sort of approach that stands a much better chance of enlisting the support of our Latin democratic friends than our current approach, which freezes them out.

Our argument over human rights certification leads no place that we should want to go: it is wrong to whitewash the Salvadoran government and it is wrong to cut that government off. But the hitch in our policy is not that we are supporting an imperfect government. It is that we are not exhausting the diplomatic means available to us to serve our essential purpose in El Salvador of seeing that, one way or another, the popular will is finally honored.