''The question is not why Nicaragua signed the agreement,'' commander of the revolution Tomas Borge said on Radio Managua Sandino (Aug. 27), ''the question is why the other Central American presidents finally agreed to sign the document.''

I have another question. Why did House Speaker Jim Wright so quickly agree to support the ''peace plan'' adopted at Esquipulas, Guatemala?

Wright is a smart man who usually knows what he is doing. Why did he join Ronald Reagan in a ''peace proposal'' only to dump it without discussion when the Central American presidents adopted a very different plan? Is it possible that Wright does not understand the important differences between the Wright-Reagan plan on the one hand and what the Sandinistas call ''Esquipulas II'' on the other? Is it possible he knows but doesn't care that ''Esquipulas II'' ignores vital U.S. interests in the region?

Wright has been caught in a bind between his Fort Worth, Texas, constituents who want to aid the contras and the vociferous, numerous left wing of House Democrats who are determined to block aid to the contras. Pressures from home promise to increase -- especially if congressional Democrats succeed in cutting off contra funding. They will get worse still when the guerrilla war in El Salvador heats up again. The pressures from the Democrats' large left wing in the House promise to intensify once the administration formally proposes legislation extending aid.

Wright, I fear, sought to smother his political problems in peace plans -- thus removing the need to vote either for or against contra aid and arranging to have the Reagan administration share the responsibility for whatever happens in Central America afterward. At first blush it looked as though Wright had succeeded in getting himself off the hook and putting Ronald Reagan on it.

I predict the maneuver will be neither good politics nor good policy. As a peace plan ''Esquipulas II'' has some fatal flaws. It does not deal with Soviet and Soviet-bloc military aid to Nicaragua, though that is a permanent threat to the stability and independence of the region. It dismantles the Nicaraguan resistance forces first and calls for free elections after. It includes no provisions to ensure compliance, no sanctions to punish noncompliance.

Even if all parties moved forward on implementation, ''Esquipulas II'' provides no assurances that the Sandinistas will not reverse all their steps to liberalization and democratization once the Nicaraguan resistance forces have been dismantled. After all, their record is not good. Quite specific promises of democracy made to the Organization of American States in June 1979 are still unfulfilled.

I doubt that the comandantes can bring themselves to permit freedom to their opponents. The comandantes are addicted to the use of force. This is why they give themselves military titles, wear uniforms, repress dissidents, set loose turbas divinas (divine mobs) to bully opposition organizations. This is why they have militarized Nicaragua. Can they -- possessing power -- restrain themselves in its use? I doubt it. Can they permit the sustained functioning of La Prensa and Radio Catholica? Can they end censorship? I doubt it.

The Wright maneuver also will not work as politics. House Democrats are trying to make it appear that a vote for contra aid is a vote against peace. But too many Americans understand with whom we are dealing in Central America. The most recent issue of Public Opinion magazine reveals that 60 percent of Americans believe the government of Nicaragua will provide the Soviet Union military bases unless the United States prevents it, that 72 percent of Americans believe the Sandinistas' success will lead to further Communist ad-vances in the region, that 50 percent believe the United States should eliminate Communism from Latin America.

It is true that a majority of Americans oppose aid to the contras, but as Everett Carll Ladd points out in Public Opinion, a majority also opposes foreign aid to almost everyone for almost everything -- which, curiously, does not prevent a majority of House Democrats from supporting tens of millions of aid for, say, Marxist Mozambique.

It is time for Jim Wright and moderate Democrats like him to give the Sandinistas an incentive to cooperate. The most effective way to reinforce the peace process in Central America is to authorize adequate military aid for contra fighting forces, and put the money in escrow until the ''commanders of the revolution'' in Managua have had the opportunity to demonstrate their commitment to democracy. This is a message that would be welcomed in Fort Worth if not in Managua.