THE AMERICAN left has an unexamined past. Like the French conservatives, who went into deep denial about their collaboration with the Nazis a half century ago, American leftists and some of their liberal allies have refused to sort out their own intimate connections with Marxist-Leninism in the 1930s, 1940s and 1950s.

In a footnote on page 725 of "Witness," his 1952 classic of American confessional literature, Whittaker Chambers explained how this came to pass. He observed, "It is not the communists, but the ex-communists who have cooperated with the government, who have chiefly suffered..." Writing at the height of the controversy about communists in the U.S. government, Chambers explained, "It is worth noting that not one communist was moved to break with communism under the pressures of the Hiss case. Let those who wonder about communism and the power of its faith ponder that fact."

For decades after Chambers wrote those words, liberals and leftists held the high ground in the dispute over whether a communist conspiracy actually existed in the United States or was simply a by-product of "the paranoid style in American politics." They came to accept that there was a foreign communist menace but never a domestic one. There were rancorous divisions on the liberal-left in the 1950s over who was a spy and who was an accused innocent, who was a secret communist political operative and who was a straightforward fighter for social justice. While anti-communist liberals and leftists ranging from Sen. Hubert Humphrey to writer Dwight McDonald condemned the communists, there was a formulaic, transparent insincerity about much of left-liberal anti-communism.

In the upmarket universities and other places where the dominant form of polite liberalism thrived, the accusers, who had named names and had pointed out the communist spies, were scorned as despicable vermin. Among more mainstream scholars, like Richard Hofstadter, the forces of do mestic anti-communism were described largely as manifestations of social underdevelopment and popular irrationality, not legitimate concern.

As the 1960s wore on, the savagery and futility of the Vietnam War discredited the anti-communist cause. By the end of the 1960s, the demonization of the anti-communists had gained currency, and not just on the far left. Everyone from Richard Nixon to Whittaker Chambers to Elizabeth Bentley, a former espionage agent who in the early 1950s had given scores of names to the House Un-American Activities Committee, were dismissed as adventurers, opportunists, cats paws of reaction, psychos, creeps, blackmailers and junior Joe McCarthys.

As playwright Lillian Hellman recalled, "The McCarthy group -- a loose term for all the boys, lobbyists, congressmen, State Department bureaucrats, CIA operators -- chose the anti-Red scare with perhaps more cynicism than Hitler picked antisemitism."

But in the last year as though from a buried, toxic waste dump, poisons, moving with the slow capillary action of history long hidden, are hiccuping up a different truth. The materials that first made their way to the surface in the early 1990s -- records from Moscow's Russian Center for the Preservation and Study of Documents of Recent History -- provided proof past peradventure that the Communist Party of the United States was subsidized by the Soviet government and used as a base for extensive espionage.

So now liberals must face the question: Was Joe McCarthy right? Could all the defiant politicians, the martyrs to civil liberties, the blacklisted teachers and entertainers, the earnest professors and sincere foundation executives have been wrong? The answer is, no and yes.

It has long been known that the Communist Party of the United States of America (CPUSA) had been paid for by the Soviet Union. But acknowledgment of even this truth has been hard to come by. In liberal and leftist circles the term "Moscow gold" was accompanied most often by derisive laughter and the riposte that it was not Moscow gold but the paid dues of FBI informants that kept the CPUSA afloat. Actually, it was both.

Now comes more from vaults of the National Security Agency. In the 1940s, the NSA had a top-secret program called Venona which intercepted (and much later decoded) messages between Moscow and its American agents. The recent publication of a batch of Venona transcripts gives evidence that the Roosevelt and Truman administrations were rife with communist spies and political operatives who reported, directly or indirectly, to the Soviet government, much as their anti-communist opponents charged. The Age of McCarthyism, it turns out, was not the simple witch hunt of the innocent by the malevolent as two generations of high school and college students have been taught.

The sum and substance of this growing body of material is that: Ethel and Julius Rosenberg, executed in June 1953 for atomic espionage, were guilty; Alger Hiss, a darling of the establishment was guilty; and that dozens of lesser known persons such as Victor Perlo, Judith Coplon and Harry Gold, whose innocence of the accusations made against them had been a tenet of leftist faith for decades, were traitors or, at the least, the ideological vassals of a foreign power.

Even moderate politicians who insisted upon the fact -- and argued that these people might have influenced U.S. foreign policy -- were scorned. Sen. Robert Taft of Ohio said, "The greatest Kremlin asset in our history has been the pro-communist group in the State Department who surrendered to every demand of Russia at Yalta and Potsdam, and promoted at every opportunity the communist cause in China until today communism threatens to take over all of Asia." Secretary of State Dean Acheson, a pillar of the establishment, concluded that Taft had joined "the primitives."

The part played by Klaus Fuchs, a high-level physicist, who had worked at Los Alamos, has been known for many years, as has the treason of the Rosenbergs. Nevertheless, for as long as the subject was a hotly-disputed controversy, it was the practice in leftist circles to scoff at the rustic notion that the "secret" of the bomb could be stolen at all. Now we know, thanks to the latest Venona transcripts, that a Harvard-trained physicist named Theodore Alvin Hall was passing secrets about the instrument which changed world politics in the last half of the 20th century.

The disaster brought on by the end of the American atomic monopoly was not lost on the more perspicacious thinkers of the time. In 1947 Bertrand Russell, the British scientist, philosopher and pacifist leader, saw the monopoly as the world's only opportunity for preventing the Soviets from working their will on much of the globe. Noting the nature of "Asiatic communism" (which American liberals were often unable to see in its fullest dimensions), he argued for forcing Moscow into a humane capitulation, even if it took a military ultimatum to do it. But, as the right eye of American politics was blind to fascism in the 1930s, the left eye could not comprehend the nature of communism -- then or later.

And where was Harry Truman? His hagiographers today present him as the plucky, courageous, little guy who stood up to world communism and led America into a new age of cosmopolitan internationalism. It is a description that millions of his adult contemporaries would have found unrecognizable. In fact, the public conduct of the Truman administration became the affirmation of people who said Truman was soft on communism. When Winston Churchill delivered his famous "Iron Curtain" speech at Fulton, Mo. in March 1946, Truman immediately disavowed the former British prime minister. Astonishing as it may seem to those who get their history from movies and TV, the American president invited Joseph Stalin to come to Fulton and give a speech presenting his side of the story. Truman actually offered to send the battleship Missouri to fetch the Soviet tyrant.

Truman soon changed directions giving us the Truman Doctrine (calling for resistance to communism everywhere), the Marshall Plan (to rebuild Western Europe) and the North Atlantic Treaty Organization (to defend it from Soviet attack). Truman instituted so-called loyalty boards in all government agencies. But he also called the investigation of Alger Hiss "a red herring," encouraging the suspicion that the government was not really addressing the communist threat.

Inevitably came Sen. Joe McCarthy to exploit this suspicion. He came to fame on Feb. 9, 1950, when he gave a speech at McClure Hotel, in Wheeling, West Va. The exact text was not preserved but reporters on the scene quoted McCarthy as saying, "While I cannot take the time to name all of the men in the State Department who have been named as members of the Communist Party and members of a spy ring, I have here in my hand a list of 205 that were known to the secretary of state as being members of the Communist Party and who, nevertheless, are still working and shaping the policy in the State Department."

McCarthy, as his subsequent history would show, knew little about communism, on this side of the ocean or the other. This loutish, duplicitous bully, who carried, not the names of Reds but bottles of hootch in his briefcase died in disgrace and of alcoholism. Yet, in a global sense McCarthy was on to something. McCarthy may have exaggerated the scope of the problem but not by much. The government was the workplace of perhaps 100 communist agents in 1943-45. He just didn't know their names.

In response to McCarthy's attack John E. Peurifoy, deputy undersecretary of state, said that in the previous three years the government had investigated over 16,000 of its employees and had failed to find a communist. "If I can find a single one, he will be fired by sundown," Peurifoy declared. The Venona transcripts contain the code names of about 200 persons, although some of these were clearly persons who had unwitting contact with Soviet agents. The Venona documents indicate that there were perhaps a dozen Soviet agents in the State Department alone. It is now clear that the Truman administration wasn't looking very hard.

The political terror of the early 1950s, in which McCarthy was to play the role of a bush league Robespierre, was set off by wider forces and conflicts than a quarrel over whether or not the Roosevelt and Truman administrations had been penetrated by foreign agents.

The cellulose to which McCarthy applied his match was the Truman administration's acquiescence to the imposition of communist dictatorships across the eastern third of Europe. While Washington policymakers argued that only another world war could stop Stalin, millions of voters of Polish, Hungarian, Estonian, Czech, German, Lithuanian, Latvian and Ukrainian extraction saw nations to which they had the closest emotional ties come under Soviet thrall, sometimes by actual arrangement with the American government or in the face of a murmured pro forma opposition by Washington.

Starting in Wisconsin, whence McCarthy hailed, the political fire storm he ignited burned brightest where these emigre populations were most concentrated. In the eyes of celebrity liberalism, those up in arms about the government's acceptance of communist ambition were the unappetizing people of the dull world of the lower middle class. They were the piano-legged babushkas of American politics, stolid Slavs and such, thick of finger and numb of mind.

In the ongoing kulturkampf dividing the society, the elites of Hollywood, Cambridge and liberal think-tankery had little sympathy for bow-legged men with their American Legion caps and their fat wives, their yapping about Yalta and the Katyn Forest. Catholic and kitsch, looking out of their picture windows at their flocks of pink plastic flamingos, the lower middles and their foreign policy anguish were too infra dig to be taken seriously.

Once a year these people would hold huge Captive Nation Day rallies in cities across the country, which Democratic politicians of taste and sensibility avoided. The only Democrats in evidence at these rallies of unstylish anti-communists were often dismissed by their social superiors as smarmy, corrupt, machine pols. Auschwitz, Treblinka, Belsen, all the Nazi concentration camps were dismantled, but the Gulag grew and left-liberals like California congresswoman Helen Gahagan Douglas and the editors at the New Republic magazine seemed not to care. Working class anti-communist voters did not fail to notice the disdain with which some of the liberal intelligentsia regarded them. The early 1950s, not coincidentally, marked the beginning of the great outmigration of the blue-collar workers from the Democratic Party.

When McCarthy and his congressional allies began to demand testimony from alleged communists about the infiltration that was real but undocumented (the Venona program then being the most sensitive of state secrets), liberals denounced them for "star chamber" tactics.

This term was apt, perhaps more so than some of the righteous liberals knew. The "star chamber" was an innovation of 16th century England when the British monarchy faced a challenge very much like that of the United States in the early Cold War. In both cases, there was a clandestine ideology, loose in the land, supported with money and military power by a foreign government. In both cases, the practitioners were secretly engaged, not just in espionage but in ordinary politics. In England, suspected Spanish agents were grilled in secret chambers about their beliefs. The grilling of suspected communists four centuries later in America was quite similar. But the many abuses committed in the star chambers in no way change the fact that the clandestine methods of the foreign power were real and dangerous.

This is the essential truth that the left end of the American political spectrum has evaded. The consequences for liberal causes have been devastating. The communists' clandestine method poisoned the politics of civil rights in the 1950s. Many people were scared off of supporting the movement because of the common allegation that it was communist-inspired. The charge could not be effectively refuted because nobody knew who the hell a communist was.

Communist underground politics also fostered the notion that domestic communism had to be fought by secret means. The CIA adopted this notion by illegally sponsoring the National Student Association. This intervention in domestic politics was, of course, a violation of the CIA charter and a menace to the integrity of American democracy. But it was accepted, wittingly by some young liberal leaders of the National Student Association. A popular phrase time at the time was "fighting fire with fire." Communist secrecy had legitimated the idea.

The communist penetration contributed to the decline of American unions. When the Truman administration imposed "loyalty oaths" to get communists out of the government, union leaders were trapped. John L. Lewis, the president of the coal miners union and a (literally) violent foe of communists in his own rank and file, resisted loyalty oaths because he understood that they would lead to a kind of political regularity that would curb the labor movement's ability to challenge its business adversaries. He proved to be right. With the reality of domestic communism downplayed, old political prejudices were passed on and unthinkingly accepted.

In our own era liberals found Ronald Reagan's characterization of international communism as an "evil empire," gauche, tasteless and embarrassing. Would they have preferred, a very, very bad empire, a wicked one or merely naughty?

As yet unexplored is the possibility that certain features in the political culture of the American left are hand-me-downs from this period. The "elitism" and didacticism that so gall its opponents may be a morphed version of the communist doctrine of vanguard leadership. The liberal penchant for government giganticism, complex bureaucracy and central planning may also have taken root in the liberal admiration of the Soviet system in the 1930s.

An adequate history of the McCarthy/Truman period, one that gives proper attention to the class, ethnic, religious and cultural antagonisms of those times, has not yet been written. But enough new information has come to light about the communists in the U.S. government that we may now say that point by point Joe McCarthy got it all wrong and yet was still closer to the truth than those who ridiculed him. Nicholas von Hoffman, a columnist for the New York Observer, is a frequent contributor to Outlook.