The surprise Reagan-Wright peace plan, which was supposed to preempt any competing Central American initiative, survived only a few days before the ominously weak agreement struck in Guatemala won over Speaker Jim Wright, the State Department and, apparently, Ronald Reagan.

That looks like the end for the contras. It betrays ominous failures in White House judgment following the Iran-contra deluge. It shows the danger of wrenching Reagan from his ideological moorings and persuading him to cross flimsy foreign policy bridges built to placate political foes. Key administration officials doubt he can ever come back to all-out contra support.

''Grave misjudgment'' was the phrase of one such official describing White House certainty that the long-awaited Guatemala agreement plan would be ''derailed'' by the Reagan-Wright plan (which itself was badly flawed). The ''misjudgment'' left Reagan-Wright with one distinction: history's briefest peace plan.

That became clear when the peacemaking speaker gave his enthusiastic approval to the Guatemala plan on the morning of Aug. 7, long before he or any administration official had read its fine print. Ignoring Reagan-Wright, he lauded the Central American plan and said the United States should support it.

The reaction inside Reagan's official family was divided. Secretary of State George Shultz was buoyed. He urged finessing all talk of new U.S. aid for the anti-Sandinista freedom fighters. Defense Secretary Caspar Weinberger and national security adviser Frank Carlucci (traveling in Europe when final details of Reagan-Wright emerged last week) disagreed.

Weinberger and Carlucci wanted Reagan to boost the contras in his televised speech Wednesday with strong language supporting their objectives and promising never to forget them (reminiscent of President Kennedy's praise of the vanquished Cuban freedom fighters after the Bay of Pigs). Carlucci counseled Reagan to support only those parts of the Latin plan ''consistent with U.S. interests,'' which is what the president said he would do yesterday.

Shultz, whose heart seems set at any cost on putting Nicaragua behind the administration, has not ruled out direct U.S.-Sandinista talks and wants Ambassador Philip Habib to negotiate for the United States in ending communist rule in Nicaragua. Career diplomat Habib is associated by other officials with the Vietnam negotiations in Paris that followed Richard Nixon's and Henry Kissinger's policies and led, through no fault of his, to Hanoi's overwhelming South Vietnam and the United States' breaking every pledge of protection.

But these officials note even those Paris accords, which ended in total communist control, were more favorable to the United States than the Guatemala plan. Although the provisions never were enforced by Washington, they at least treated both sides the same on post-cease-fire arms aid. The Guatemala plan would end aid only to ''irregular forces'' -- in Nicaragua that means the contras.

Indeed, the plan appears to guarantee Sandinista President Daniel Ortega's remaining in office at least until January 1991. Its supposed free-elections timetable complies with the present Sandinista constitution. Long before that time, the contras presumably will have withered away as a fighting force.

The Guatemala plan is consciously tilted toward regimes now in power, including communist Nicaragua's. That explains support from El Salvador's President Jose Napoleon Duarte, who gets the same protections against communist insurgents besieging his regime that the Sandinistas have against U.S.-backed contras.

''Let's face it,'' an administration realist told us, ''the presidents who wrote this plan acted in their own interests as incumbents, not as anticommunists.'' But their safety is illusory. Duarte's communist foes, counting on renewed support from a guaranteed Sandinista regime, say the Guatemala plan does not apply to them.

This flawed plan finds Wright linked with Shultz, who is more powerful than ever inside the White House following the Iran-contra hearings. Their ally is chief of staff Howard Baker, who wants to defuse Nicaragua to facilitate a superpower summit with Mikhail Gorbachev. Baker and Shultz are deciding all national security issues in the light of their effect on the summit. Against this phalanx, Republican protest is scattered and feeble.

Pessimism is rising in the Pentagon about halting communist penetration of the hemisphere and about the future of the contras as agents of that mission. When invited conservatives met Baker (and, in a brief cameo appearance, Reagan) in the White House Wednesday, Baker cautioned them: stay cool until Sept. 30. That's the date current military aid money for the contras runs out.

Baker implied that will leave ample time to replenish contra aid coffers, but the facts suggest otherwise. They suggest that in the fog of words, delays, half-baked plans and sellouts of the kind that lie ahead -- similar to those that followed the Paris accords on Vietnam -- the contras' hide may soon be tacked on a Kremlin wall next to South Vietnam's.