Who won the Vietnam war? Richard Nixon, the former president, says we did, and Ronald Reagan, the current president, says he agrees with him. The question could be debated forever, especially if you don't define what you mean by "won." But the American people have already supplied the answer. We lost in Vietnam. The proof of that can be found in Nicaragua.

There, on the northern border, are some 15,000 so-called contras -- organized and financed by the CIA. According to the president, these men are the "moral equivalent of the Founding Fathers." He has compared them to Lafayette and he talks of their opponents with utter contempt. The Sandinistas, he says, are bitter- end communists, thugs, and their regime is one of the most repressive in the world -- a menace to the region, a danger to the United States.

But he can't get Congress to give the contras $14 million in military aid.

Step back and take a look at what we're talking about. In Washington, $14 million isn't even money. It's what some agencies probably spend on typewriter ribbons or, if you will, on coffee makers. It's petty cash, pennies. At the Pentagon $14 million is a tip left on the table for General Dynamics.

Try as he might, the president cannot get Congress to appropriate even so small an amount to the contras as military aid. Republican congressional leaders went out, counted votes and came back with their heads shaking "no." It could not be done. Money is not the issue and neither are the qualms about waging an undeclared war. What thwarts Reagan on Nicaragua is the sense that we have been down this road once before. It leads, in the end, to helicopters snatching Americans off Saigon rooftops.

The American consensus on the matter is so firm that not even the strong, nearly hysterical, convictions of a very popular president can budge it. On the MX missile, for instance, Reagan personally turned the tide in Congress and won a victory that simply was not there when he began his effort. In fact, members of Congress who feel that the MX is a turkey of a weapon -- expensive, outdated and destabilizing to boot -- caved in when the president brought the full weight of his popularity down on them. Yet, when it comes to Nicaragua -- by Reagan's standards a much more immediate danger -- Congress got backbone. It said no.

Ironically, Reagan himself may have contributed to his own defeat. He shows every evidence of not having assimilated the lessons of the Vietnam war. He knows enough, of course, to rule out the use of American troops in Nicaragua but his oaths lack conviction. That's because in every other way Reagan sounds Johnsonesque in his pronouncements about Nicaragua. As Lyndon Johnson did with Vietnam, Reagan so exaggerates the danger Nicaragua poses and the situation there that he loses credibility. Who believes that the Sandinistas have created a gulag? Who thinks that, in a world full of stinking governments, the one in Nicaragua is among the worst? Who believes that a nation of 3 million poses a threat to its region -- not to mention San Diego?

All this hyperbole in the name of anti-communism seems to give Americans the Vietnam willies. The feeling is based on a clear-eyed assessment of the situation. Everyone knows that $14 million is not going to do the trick in Nicaragua and that "the trick" is not, as Congress was told in a secret report, to "moderate" Sandinista behavior, but to topple the regime. Ronald Reagan has been talking about communists and communism for too long for anyone to think he wants to settle for "moderation" -- whatever that is.

Vietnam made sophisticates out of Americans. For the political left, the war and its aftermath took the romance out of revolution. Few call the Sandinistas "agrarian reformers," defend their trampling of civil liberties or think they need the excuse of American hostility to be hostile to America. As for others, the romance has gone out of anticommunist crusades that can cost American lives and that seem, even when lost, to have no affect on American security.

Who won in Vietnam? The answer is neither in a book by Nixon nor a remark by Reagan, but in congressional policy toward Nicaragua.