Patrick J. Buchanan, the White House communications director, and I have one thing in common: neither of us has ever been in Nicaragua. We also have one difference: while I am prepared to concede that people with greater knowledge of Central America can and do have honest doubts and disagreements about the best U.S. policy toward that nation, Buchanan has only scorn for those who dissent from his second-hand wisdom.

Buchanan is both the architect and the cutting-edge advocate of the hard-line, hard-sell White House push for $100 million of military aid and supplies for the contras fighting the Sandinista government forces in Nicaragua. The aid package is scheduled for a vote in the House later this week.

Earlier this month, he laid into the opponents of military aid with a zest that showed he has lost nothing off his spitball since he was coining phrases for Spiro T. Agnew in the early 1970s. Those who resist the push for an American-financed civil war in Central America are, in Buchanan's choice phrases, "the liberated nuns and Marxist Maryknolls, the journalistic camp followers and tenured professors anxious to wow the coeds with how they picked coffee beans for the revolution."

But the real enemy is "the national Democratic Party" which, Buchanan said, already has become "with Moscow, co-guarantor of the Brezhnev doctrine in Central America . . . (and) with the vote on Contra aid . . . will reveal whether it stands with Ronald Reagan and the resistance -- or Daniel Ortega and the communists."

When the author of these fiery words came to lunch with a group of journalists the other day, he was not in the least defensive about lecturing members of Congress who have reached a different conclusion from their travels to Nicaragua and meetings with contras and Sandinistas. "I get information from all the agencies of government," he said. "I have as much or more than the president. . . ."

Not wishing to challenge such an authority directly, one of the reporters asked why the leaders of major Latin American countries, with borders closer to Nicaragua than ours, seemed less enthusiastic about an attempted military "solution" to the problem.

The foreign ministers of eight Latin American nations came to Washington in February and met with Secretary of State George Shultz "to urge that the administration's push for aid to Nicaraguan rebels be replaced with a push for a regional peace treaty in Central America," as The Post reported. One Latin diplomat, according to my colleague, Joanne Omang, said their plea met "a stone wall" of resistance.

How could the United States hope to make a success of a policy that did not command their support, Buchanan was asked.

His reply was that "privately" some of them were more supportive of U.S. policy than their domestic politics allowed them to be in public. That sounded interesting, so we asked more questions: Which countries were more supportive in private? President Reagan might whisper that answer to leaders of Congress, he replied, but it would be "totally inappropriate" for him to give it to us.

Was he saying that they supported military aid? No, he couldn't say that. Well, what had they said privately? That, he was not in a position to answer. "All I can tell you is that leaders of our government say they've been told some things in private that are different."

This level of argument would be laughable were it not employed by the official spokesman for an administration that is calling critics of its policy dupes of the communists. When the coyness and the calumny are combined, they become contemptible.

I do not profess to know which of the several bad options available offers the best chance of changing or deflecting the Sandinista government, which is by all available evidence hardening its internal police-state practices and increasing its external mischief-making. Last year, Reagan imposed economic sanctions on Nicaragua and sent the contras nonlethal aid. That doesn't seem to have worked.

Now he is saying that $100 million in guns and ammunition and other supplies for an outnumbered set of soldiers with a record of committing atrocities of their own will turn things around. That's possible, but implausible. You have to be a real optimist to believe that an American-financed and American- equipped military force, operating without the public support of the major Latin American countries, can somehow establish itself as the legitimate government of a country such as Nicaragua, where the United States once landed Marines to protect its commercial interests and where we propped up the brutal dictator the leaders of the current government overthrew.

Henry Cisneros, the mayor of San Antonio who was appointed by Reagan to the Kissinger commission on Central American policy, said Hispanics here and in the lands to the south "know the history too well of the role we have played in the region . . . to be stampeded" by the arguments of the administration.

But what does Cisneros know? He's been to Nicaragua. He's a Democrat. Pat Buchanan suffers no such disabilities. Let's let him decide.