Neraly 30 years ago, a California longshoreman, Eric Hoffer, wrote a small book that remains today one of the most provocative and important works of the last generation. In examining what he called "the true believer" mentality and its impact on mass movements, he said:

"All mass movements . . . irrespective of the doctrine they preach and the program they project, breed, fanaticism, enthusiasm, feverent hope, hatred and intolerance; all of them are capable of releasing a powerful flow of activity in certain departments of life; all of the demand blind faith and singlehearted allegiance. All movements, however different in doctrine and aspiration, draw their early adherents from the same types of humanity; they all appeal to the same types of minds.

"Though there are obvious differences between the fanatical Christian, the fanatical Mohammedan, the fanatical nationalist, the fanatical Communist and the fanatical Nazi, it is yet true that the fanaticism which animates them may be viewed and treated as one."

Without realizing it, Hoffer was describing the elements that make up what is probably today's most significant mass political movement -- the so-called Moral Majority, or Christian Right. Much has been written already about these new old-fashioned zealots. In the emotional and volatile politics of 1980, much more attention needs to be paid them.

When he came to Washington he was a rarity -- a minister in politics, a cleric in Congress. And John Buchanan brought with him special credentials that made his election then notable. He was elected as part of the supposed emerging new Republican majority sweeping the Old South in the mid-'60s. In the 1964 presidential year, when conservatives were saying they finally were offering the American voters a real choice, not an echo of liberal policies past, Buchanan ran as a member of the Goldwater GOP faction. Although Goldwater lost nationally, Buchanan won a congressional seat in the Alabama district that includes Birmingham and the surrounding area.

His background could have qualified him for inclusion in one of Sinclair Lewis' tales of small-town American life -- he had been a Mason, Kiwanian, Navy veteran, county GOP chairman, director of finance and public relations for the Republican Party in Alabama, and long active in church work. For 10 years, he had been a Baptist minister, a graduate of the Southern Baptist Theological Seminary. Once in Washington he continued his church work, as interim minister and Sunday school teacher at a small Baptist congregation.

And he voted right.

When the Vietnam war was at its peak, he was one who called for greater military efforts: he favored taking the wraps off restricted bombing targets in North Vietnam. When Richard Nixon began to be engulfed by Watergate, Buchanan was one of his strongest supporters. His record was solidly conservative. He stood with the National Rifle Association against legislative efforts to limit the sale of firearms, he was the author of a constitutional amendment to permit voluntary prayers in public schools, he led what was believed to be the first attempt to put Congress on record against persecution of Christians in the Soviet Union, he spoke repeatedly in his addresses about the menace of atheistic communism.

To those who worried about ministers in politics, Buchanan had a ready answer. On one occasion when that question arose in his congressional office, Buchanan got up from his desk, walked quickly over to a cabinet and pulled out a large, worn Bible. "See here," he said, after opening the Bible to a certain passage, "It says the magistrate is 'God's minister.' That's me."

Buchanan was no mossback, and he changed with the times, but no one could ever accuse him accurately of being anything other than a conservative Republican representative from northern Alabama. He ran and won, every time after he first came to the Congress nearly 16 years ago.

Every time, that is, until a few days ago, when John Buchanan lost the GOP primary in Alabama. He was overwhelmed by the forces of the "Moral Majority" who vigorously backed a far more conservative candidate. They succeeded in persuading a majority of those voting that Buchanan, the ex-Baptist minister and Sunday school teacher, was too liberal. He was attacked for his support of the Equal Rights Amendment and for his moderate positions on blacks, who represent a third of his congressional district. He was also portrayed -- inaccurately -- as being against prayer in schools, and not "pro-family" enough.

By wedding the basic hard right-wing political issues to religious fundamentalist ones, the "moral majority" forces made it seem that a vote against their own man was close to being immoral.

As one of Buchanan's campaign aides said later, "For them it was a holy crusade to dump John." When the election was over, the Alabama papers reported, the anti-Buchanan forces held a prayer meeting. They thanked God for the victory, terming it the "will of God."

"How do you fight that?" the same aide said.

The election results apparently stunned Buchanan's people. Their polls had not picked up the move against them, and they were confident that by getting out their normal vote they would be victorious. They did, in greater measure than before, but their opponents outorganized, outworked and outvoted them. "They caught us completely by surprise," the Buchanan operative remarked. "We were probably beaten early on and never realized it."

The "Moral Majority" is a misnomer. It is the militant minority. Whether Eric Hoffer was correct when he said, "Faith in a holy cause is to a considerable extent a substitute for the lost faith in ourselves," is highly debatable. But as this latest example shows, the millitant minority can take control when zealously motivated. As Hoffer knew long ago, true believers are a powerful force when aroused.