President Reagan, with timely help from the Sandinistas, is well on the way to winning congressional approval of military aid for his beloved contras. But his victory is coming at considerable cost to administration credibility.

Handed the gift of a Nicaraguan incursion into Honduras, administration officials didn't know what to do with their good fortune. They garbled accounts and statistics at various briefings, then blamed the news media for the result. Less than a month after White House Communications Director Patrick J. Buchanan charged that Democrats opposed to aiding the contras stood with Nicaraguan President Daniel Ortega "and the communists," White House spokesman Larry Speakes accused the news media of Sandinista sympathies.

In addition to casting the administration as a sore winner, such excessiveness may inadvertently reflect the private doubts of more thoughtful officials about the contra enterprise. Forced to address these doubts for tactical reasons during the Senate debate on contra aid, Reagan signed a letter to Sen. Sam Nunn (D-Ga.) pledging that contra troops would be subject to civilian control and required to respect human rights.

Reagan, traveling to California at the time, may not have seen the letter issued in his name or known that it was a backhanded admission that contra troops have alienated many Nicaraguans in whose name they fight. But some U.S. military and national security advisers privately give the contras low marks, and say their capability and conduct bear little resemblance to the glowing portrait that Reagan paints of the "freedom fighters."

In an administration where analogy too often substitutes for thought, the contras have been likened to the Founding Fathers, the Hungarian freedom fighters and the French Resistance, while the situation in Nicaragua has been compared to conditions that existed in Haiti and the Philippines before dictators were overthrown.

Reagan, of all people, should know better. He has long recognized that communist regimes differ from other dictatorships in ruthless and effective totalitarian control of their populations. He also must realize that the Sandinistas will not enter into power-sharing negotiations merely because they are being harassed by a guerrilla force. Reagan's policy promises a protracted and inconclusive war that could still be raging when he leaves office.

Democrats, more accomplished at criticizing Reagan than devising policy alternatives, say this war will create the conditions for eventual intervention with U.S. troops. As usual, the critics fail to give Reagan any credit. The president, who has a sound grasp of domestic political reality, fully recognizes the unpopularity of U.S. intervention and has learned the Vietnam lesson that such public support is essential for victory.

Unfortunately, Reagan is less realistic about the contras' attitude to the democratic verities he celebrates. He has refused to become involved in the messy complexities of Nicaraguan politics, including the contras' inability to unite with other anti-Sandinista forces. While Reagan is often accused of harboring an apocalyptic view of the Sandinistas, the greater danger is that he is a romantic who looks at the ill-trained and not necessarily democratic contra forces and sees the continental armies at Valley Forge.

This romanticism is dangerous because it leads Reagan to claim more for his $100 million contra aid package than it is likely to accomplish. It leads him to imply that a war which he sees as critical to the United States can be fought by others and won on the cheap. It leads him to another tunnel with no light at the end.

There is a good case to be made against the Sandinistas, and a case to be made for the contras, too. The case is that their fight is ultimately our fight, and that it will cost billions of dollars, not millions, to win it. It is a case that could be made by discarding fanciful analogies to other wars and acknowledging that the contras must be trained in democratic arts as well as martial ones. The letter to Nunn is a start, if Reagan means it.

Reaganism of the Week: Asked by Barbara Walters on an ABC special last Monday whether he would ever make another film, the president said: "It seems hard to me to believe that I could. And I think I have a feeling that maybe it would look like I was exploiting the office that I'd held." wars and acknowledging that the contras must be trained in democratic arts as well as martial ones. The letter to Nunn is a start, if Reagan means it.

Reaganism of the Week: Asked by Barbara Walters on an ABC special last Monday whether he would ever make another film, the president said: "It seems hard to me to believe that I could. And I think I have a feeling that maybe it would look like I was exploiting the office that I'd held."