Right after the House vote on the Boland amendment, Speaker Tip O'Neill was in his private office doing what he often does -- a favor for a friend. Still smarting from the clubbing he took on a move that would have ended CIA involvement with the Nicaraguan contras, O'Neill was making a tape for a fund-raiser for Mo Udall of Arizona.

O'Neill did not want to talk about what had just happened. He read from a statement hastily prepared by his staff, which pointed out that President Reagan had won his stunning victory only by repudiating military aid for the rebels, criticizing their conduct, agreeing to negotiate with the ruling Sandinistas and disavowing any intention of overthrowing their government.

His heart was not in it.

"I just can't explain it," he said.

For O'Neill, it was a galling personal loss.

He had thrown all of his weight into the fight against his fellow Irishman in the White House, casting aside his usual diffidence on foreign policy questions. But on Nicaragua, he thought he knew, firsthand, more than the State Department or the White House. A boyhood friend had gone to Nicaragua as a Marine and gotten stabbed "for United Fruit." An aunt, a Maryknoll missionary, had assured him that the Sandinistas, whatever their political philosophy, were making a better life for the common people of Nicaragua.

But the House, which seven weeks ago unexpectedly defied the president on any aid for the contras, was nervous. O'Neill knew it and tried to make his colleagues nervous on a larger scale. Against talk of appeasement, compromise and Marxist-Leninism on our doorstep, he had hardily responded that intervention would lead to war. He thought the warning was a powerful counterweight against Nicaraguan President Daniel Ortega's trip to Moscow, and against Democratic fears of being seen as "soft on communism."

At his news conference before the session began, O'Neill elaborated on Reagan's martial fantasies, which he thinks are the roots of the policy.

"He is not going to be happy until he has our Marines and our Rangers down there . . . ," O'Neill said. "He can see himself leading a contingent down Broadway with paper flying out the windows, with a big smile on his face like a kind of 'Grade B' motion-picture actor coming home the conquering hero."

He also recalled Reagan's telling him about the glorious day he had pictured in Beirut, "with people waving handkerchiefs for the Marines who had unified their country."

"It's unbelievable," O'Neill mused. "But that's the way he talks, and that's the way he thinks."

But Reagan carried the day, 232 to 196. Fifty-eight Democrats deserted O'Neill and his best pal, Edward P. Boland (D-Mass.), chairman of the House intelligence committee.

For O'Neill, the most painful moment of a black day may have been the defection of John P. Murtha (D-Pa.). He befriended Murtha, a huge, blunt, assertive Vietnam Marine veteran.

Murtha made one of the show speeches, an emotional tirade about the wimps in Congress who had lost Vietnam by sending mixed signals.

O'Neill stood alone in the back of the chamber, his bulk draped over the brass railing, not wanting war and looking the picture of woe as Murtha spoke about people who had "fought in the mud, who had water up to the waist."

The Republicans were in rapture, and their leader, Robert H. Michel of Illinois, principal architect of the "humanitarian" aid bill, took a front-row seat for the affair. When Murtha stopped shouting, Michel rushed forward to shake his hand.

O'Neill was heartscalded by the betrayal.

"He is one of my dearest friends in the House," he said of Murtha. "I am upset. I am very, very upset with him.

"And McCurdy," he added, referring to Dave McCurdy (D-Okla.), who joined Michel in tailoring the contras' aid, "he put the knife in us. I put him on the intelligence committee because Eddie Boland asked me to. What does that tell you about his judgment?"

Dolefully, he said that the members voted against their constituents, who, polls show, want no part of Reagan's quarrel with the Sandinistas. And it wasn't Ortega's trip to Moscow. After all, Indian Prime Minister Rajiv Gandhi, who also went to see Soviet leader Mikhail Gorbachev and take money from him, was invited to address a joint session of Congress -- "and at the request of the president," O'Neill noted.

"I don't know," he said, obviously crushed by multiple treacheries. "I can't explain it. They're afraid. They're afraid of Ronald Reagan."