President Reagan is doing a rhetorical flamenco on Nicaragua, with no end of foot-stamping, shouting and whirling about. It's quite a show, but where is the audience?

A certain amount of hyperbole is understandable, even essential, for a public figure on the warpath, but Reagan's excesses on the subject of the "contras" -- the mercenaries paid by the Central Intelligence Agency to shoot up the countryside -- ought to be stopped, if only out of respect for the English language and American history.

He started out two weeks ago by calling them "our brothers" and comparing them to Lafayette and Kosciusko. Last Friday night he claimed that they are "the moral equivalent of our Founding Fathers and the brave men and women of the French Resistance."

If someone doesn't stop him, he'll be calling for their canonization. And that would be exceptionally awkward in view of a report by America's Watch, a human rights organization, which depicts his heroes as thugs who kill defenseless women and children and burn villages for the fun of it.

Reagan is apparently under the impression that he can rally the world to his view that the Sandinista rulers of Nicaragua are brutal and repressive tyrants who have invaded their native country and turned it into a Soviet state. Who believes him except the members of the Conservative Political Action Conference, probably the one group in America that didn't squirm with embarrassment to learn that our First Citizen has confused Washington, Jefferson and Madison with ex-Somoza guardsmen and other contras?

Does he really believe that he is winning people over in his crusade to make the Sandinistas say "uncle?"

Foreign ambassadors are summoned to the State Department for briefings by officials who solemnly assure them that Reagan's Nicaragua policy is gaining ground in Congress. If true, it is Washington's best-kept secret. Who but the people saying it think that his request for $14 million is victory-bound?

Are the American people lining up behind the Gipper in his scrap with Managua? Not so you'd notice it. A Washington Post poll shows 70 percent of the voters opposed to a U.S.-backed overthrow of the Sandinistas.

National security affairs adviser Robert C. McFarlane insists that being beastly to the Sandinistas is a winner in Europe. But six members of the Dutch, Italian, West German, British and Irish parliaments are in town this week to say otherwise. Their leader, an energetic representative of the Dutch labor party named Evelyn Herfkens, says they represent 600 other members of European parliaments who think that Reagan is talking through his hat about Nicaragua.

Those countries sent observers to the Nicaraguan elections and subscribe to the conclusion of French Foreign Minister Claude Cheysson: "President Reagan has described the Nicaraguan elections as a farce, but in reality they were very correct."

Reagan's strenuous attempts to make Nicaragua a pariah nation are falling flat. The European Economic Community meeting in September was told by Secretary of State George P. Shultz to exclude Nicaragua from its regional economic development plans for Latin America. They told him to go away.

The Dutch government officially deplored the U.S. withdrawal from the International Court of Justice in the matter of the mining of Nicaraguan harbors. Other European nations have registered disapproval of contra activities that have destroyed rehabilitation projects they have set up in Nicaragua.

The Irish stubbornly resist the Reagan policies. Their leader, Garrett FitzGerald, gently told Reagan to his face -- during last year's triumphant tour of his ancestral country -- that he was going at it wrong in Nicaragua. Recently, Nicaragua's deputy foreign minister, Sergio Ramirez, visited Dublin and was received by the prime minister.

In London, Ramirez was granted an audience with Prime Minister Margaret Thatcher, Reagan's self-described "greatest fan," who failed to come up with a single effusion for his Nicaraguan stance on her recent visit here.

Perhaps Reagan was counting on the support of America's conservative Roman Catholic bishops, his splendid allies in his reelection campaign. Alas for those hopes: Last week's papers and television reports carried a picture of Nicaraguan President Daniel Ortega offering a new peace plan, with Archbishop John J. O'Connor of New York, the most rigid conservative of the U.S. church's hierarchy, by his side.

The president has claimed that Sandinista slights to the Catholic Church and the pope are especially intolerable to him. But if O'Connor -- who offered to be an unofficial "bridge-builder" -- can handle it, Reagan is a bit isolated.

You'd think the old trouper would notice that the theater is empty and close the show.