About a month ago, a letter was sent to 30 prominent friends and supporters of the leftist weekly, The Nation, which had earlier published an article by Gore Vidal that was perhaps the most blatantly anti-Semitic outburst to have appeared in a respectable American periodical since World War II.

These 30 people were asked whether they had seen fit to protest the article, either in private or in public. Of the 30, 21 never responded. Of the nine who did, only six expressed disapproval of the article. The other three all voiced indignation not at the article but at the letter of inquiry, and one of them associated himself entirely with Vidal's sentiments.

As it happens, my wife, Midge Decter (who runs the Committee for the Free World), and I were the main targets of Vidal's diatribe. But the vile accusations he made against us were so obviously directed at all American Jews who support Israel, which means the vast majority of the Jewish community, that even some of our worst enemies were horrified.

Vidal's main point is that most American Jews are "Israeli fifth columnists" who "stay on among us, in order to make propaganda and raise money for Israel." Yet the full flavor of his piece cannot be conveyed by citing even this libelous accusation of treason or the incredibly impudent statement that Jews born in the United States are only living here on sufferance as guests and had therefore better shut up about "the politics of the host country." Vidal's every word is drenched in hatred of Jews, whom in the best traditions of anti-Semitic thinking he portrays as all-powerful conspirators manipulating "us" to further their own nefarious purposes.

That Gore Vidal is eaten with ferocious anti-Jewish feelings is not news. It has been obvious ever since he began complaining back in the early '60s that "the Jewish literary establishment" was -- again in its all-powerful way -- working to prevent him from being recognized as the great writer he imagines himself to be.

Nor is it particularly troubling that a given individual should be an anti-Semite. There have always been anti-Semites and there probably always will be.

What is troubling, however, is that a magazine professing devotion to liberal values should be willing to print an article that, as an irate letter to The Nation rightly said, would have been at home in one of the anti-Semitic sheets put out by the Nazis in the 1930s. And what is even more troubling is that, unlike the writer of that letter, most of The Nation's prominent friends and admirers have been unwilling to protest.

This marks an ominous new stage in our public discourse. Forty years ago, the sight vouchsafed by Hitler's death camps of where anti-Semitism could lead produced so great a revulsion against it that anyone harboring anti-Jewish attitudes could only articulate them in public at the price of being shunned. Thus for a long time, no periodical aspiring to respectability, and least of all a liberal magazine, would conceivably have published an article like Vidal's.

But with the Six-Day War of 1967, anti-Semitism began creeping back into public discourse and especially on the political left, under the guise of anti-Zionism. Because it is possible to criticize Israel without being anti-Semitic, it also became possible for anti-Semites to get away with putting all the old lies about the Jewish people back into circulation through the simple expedient of pretending they were only talking about the policies of the Israeli government.

Additional cover was conveniently provided by the fact that a number of these anti-Semites posing as critics of Israel were themselves of Jewish origin. But there was nothing new about this either. From Karl Marx to Noam Chomsky -- and, for that matter, to the current editor of The Nation -- anti-Semitic and self-hating Jews have been a familiar presence in left-wing circles.

Vidal, too, hides his anti-Semitism behind a supposedly anti-Zionist position. But in his case the pretense is so thin that his fellow anti-Zionists might have been expected to denounce him for fear of seeing their own position disgraced by association.

And indeed, Geoffrey Stokes, the press critic of the Village Voice, whose hostility to Israel (and to me) is only slightly less virulent than Vidal's, nevertheless hastened to attack his article as an "anti-Semitic screed."

On the other hand, Tom Wicker of The New York Times and Roger Wilkins of the Institute for Policy Studies, who see a racist under every bed, claim they do not even consider Vidal's article anti-Semitic. (I wonder how they feel about "The Protocols of the Elders of Zion.")

Nor was there any great outcry from Jewish liberals who have been insisting that hostility to Israel and to Jews generally is not a necessary component of the contemporary left-wing world view. Even the two or three who have spoken out have used language so mild that one might think Vidal had been guilty of nothing more than a slightly intemperate polemic, or that The Nation, in spattering its readers with this unprocessed sewage, was merely demonstrating the "feistiness" for which it is so often praised.

For the rest, there has been silence from The Nation's friends and admirers. It is a silence as deep as the moral pit into which The Nation itself has fallen in welcoming the unabashed return to American political discourse of a murderous poison against which the only antidote is the revulsion of decent people.