In the end, the crucial vote for the AWACS sale to Saudi Arabia was cast by a senator named Cohen, who rationalized that it would be good for the Jews to lose--which is hardly a new idea for them.

William S. Cohen of Maine, son of an Irish mother and a Jewish father, got to the Senate because he defied one Republican president, Richard Nixon. But he capitulated to another, Ronald Reagan, on an arms sale that he obviously thinks is both bad and wrong because, he said miserably, the defeat of the AWACS sale would cause a "backlash" against Israel and American Jewry.

He believes the Saudis "are as moderate as Yasser Arafat," that Israel deserves our unwavering support. But, rather than "place the seed of doubt in the American people," he switched his vote.

On Monday at the White House, he was told face-to-face by the president that Israel's "qualitative and quantitative" weapons margin would be maintained. Upon that guarantee of a continued arms race in the world's most dangerous neighborhood, in other words, he was won over.

From the beginning, through senatorial hand-wringing and presidential arm-twisting, the threat of anti-Semitism has hovered over the discussion. Sen. Mark O. Hatfield (R-Ore.), who was serenely opposed from Day One because he votes against all arms sales, observed to a group of reporters that he thought the issue had caused anti-Semitism to surface. It was reflected in his mail, in snide comments from constituents.

"It's always there," he said sadly, "but people have been more open about it lately."

The president set the "Reagan or Begin" tone in his last press conference when he said: "It is not the business of other nations to make American foreign policy." Richard Nixon echoed it when he blamed "intense opposition by Israeli Prime Minister Menachem Begin and parts of the American Jewish community" for resistance. Other advocates hinted the Jews would be better off with the "inordinate" influence of the Jewish lobby visibly decreased.

"I pray to God you lose," said Sen. Orrin G. Hatch (R-Utah) to Tom Dine of the American-Israeli Political Action Committee yesterday morning. Hatch, of course, seized on the death of Egyptian President Anwar Sadat as an excuse to switch sides.

Rep. Barney Frank (D-Mass.) calls it all "the worst kind of anti-Semitism--"what they're saying is that we don't have the right to speak out."

The most conspicuous defector from the Israeli side was Sen. Roger W. Jepsen (R-Iowa), a silver-haired, Bible-reading ex-insurance man. No one had been in more vehement opposition. "I am a Christian," he declared at an AIPAC banquet in May. "That is why I am for Israel. This sale must and will be stopped."

But on Monday, he had made his peace with Ronald Reagan. No, he said, sitting in the declaration chair in the Senate gallery, he did not think Saudi Arabia was any more stable. "Nothing has changed, except me," he said lamely.

Jepsen is an arresting convert because he is a dear and close friend of the Rev. Jerry Falwell, who noisily befriended Israel earlier this year after another Moral Majoritarian, the Rev. Bailey Smith, had jarringly announced that "God Almighty does not hear the prayer of a Jew."

Last month, Falwell embraced Menachem Begin at Blair House. When Begin phoned his curious new ally after bombing the Iraqi nuclear plant in June, Falwell assured him that "God deals with nations in relation to how nations deal with Israel."

Falwell, like Jepsen, was out front early against the AWACS sale. On a Phil Donahue show in April, Falwell brushed aside queries about school prayer and abortion and said, "Ask me about the Saudi arms sale." It was, he said, not to be borne.

But the voice of the Moral Majority has been strangely silent since then. Last Monday, Falwell's name showed up in an anti-AWACS newspaper ad, but the usual clamor he can raise--the mail, phone calls and fiery statements--was not heard.

He did nothing to sway the votes of conservative senators he helped elect. He calls Sens. John P. East (R-N.C.), William L. Armstrong (R-Colo.) and Jepsen "my boys," but he did not trouble to call them on behalf of his friend Menachem Begin.

It happened that on the day of the AWACS vote the final session of the Holocaust International Liberators Conference was being held here. The worst story of modern times, the official anti-Semitism that led to the extermination of 6 million Jews, was retold by victims, by soldiers who liberated them, by officials who saved a handful of those headed for the gas chambers. Middle-aged men and women showed their souvenirs of horrors compounded by the world's silence. "It will haunt me, and I want it to be so," said Jan Karski, who had been a courier for the Polish underground.

Menachem Begin, that pushy, maddening man who uses bombs and bombast, is, as he never allows us to forget, a survivor of the Holocaust. He came out trusting no one.

Now that he sees what friends such as Cohen, Jepsen and Falwell will do to Jews to save them from anti-Semitism, he may feel he is entitled. Or he may agree with Cohen that for Israel it was a "no-win" situation. The Jews are familiar with that kind.