During Ronald Reagan's first presidential campaign, I would read about his reputed ability to polarize and find it hard to believe. These reports came from California, and while Californians obviously knew the future president best, what they said lacked credibility. Ronald Reagan, say what you will about him, seemed to be a sweetheart of a guy.

Not any more. The secret held by some Californians is now shared by the rest of us. There is a touch of the demagogue to Ronald Reagan, a willingness to brush past the truth and go straight for the gut. He can be careless with facts, sly in the way he misuses words, willing to repeat a falsehood or disputed fact until it is buffed into rhetorical fool's gold. This is the propagandist at his best. It is a president at his worst.

Nicaragua is the issue where it has all come out. Here we have Reagan on communism, which, along with lower taxes and smaller government, is one of his core issues. Of course, communism is important, and Reagan is entitled to feel strongly about it. But he is also obligated to stick to the facts, to what he knows and to command the networks and the front pages of newspapers, if he must, but to do so with dignity. Nothing cheapens the presidency as much as cheap rhetoric.

The leaders of Brazil, for instance, wonder what in the world the president was referring to when he said their "radicals" were receiving training in Nicaragua. Never mind. It made for a good story. Another good story is the accusation that Nicaragua under the Sandinistas is an anti- Semitic state. That charge has been investigated by Jewish organizations, journalists, even the State Department, and found by most to be baseless. At best, the issue is in dispute.

Reagan charges that "top Nicaraguan officials are deeply involved in drug trafficking." But earlier this year a spokesman for the Drug Enforcement Administration said there was no evidence to substantiate that claim. Reagan characterizes the Sandinistas as beasts, abusers of human rights -- thugs and druggies. Nicaragua is not exactly Switzerland, but when it comes to human rights violations and the willingness to smuggle drugs, it's the contras who are the champs of the region. Reagan says the contras themselves admit they will spread their revolution, but the magazine article he cited actually said somehing different.

All these allegations are beside the point anyway. If drug smuggling is the issue, we should invade Colombia tomorrow. If state-sponsored anti-Semitism is the issue, then we should have destabilized Argentina under the generals. If human rights is our concern, we ought to put the cuffs on Ferdinand Marcos immediately and, at minimum, redirect the contras to Chile. Would you care to compare Managua's human rights record with Santiago's?

Reagan does not pause to consider such matters. He'll do the analysis; what he wants from us is emotion. Which side are you on -- ours or theirs? Brother Patrick Buchanan, taking Joe McCarthy's old tar brush out of retirement, draws the line, and Donald Regan, smugly satisfied, praises Buchanan for getting everyone's attention -- like yelling fire in a crowded theater. This time the fire is a cancer that's heading our way. Only the contras can stop it.

But what if the contras fail -- as they most likely will? What then? Will the next test of Americanism be the willingness to send more aid and then more aid? Will it matter then that some Nicaraguans -- but probably not the government -- desecrated a synagogue? Will Buchanan roar yet again on the pages of The Post, defining loyalty as the willingness to send troops? And will the president produce another picture of a Nicaraguan official taking a crate from a plane? For one crate, we aid the contras; for two we go to war. Today the contras. Ma?nana Managua.

What should have been a momentous foreign policy debate degenerated into a brawl about communism and loyalty -- not about what happens if, after millions are spent on the contras, noth gained. Questions about the future got lost in passions of the present. Yesterday's vote notwithstanding, someday we may look back from a quagmire of Nicaragua and wonder how we got bogged down. The answer will be simple. The president said history would be the judge -- and then framed the issue so it was hard for us to do the same.