I AM STANDING on a Washington street corner with a diplomat from one of the Arab nations. We have just had lunch and we are walking together, talking American politics. The results from the Illinois Democratic primary mystify him. He cannot understand how Kennedy lost. What has happened to this Jewish vote he has read so much about?

It never existed, I say. He looks surprised, and then I quickly add that I am kidding a bit. But I am not kidding when I say that it has been exaggerated and written about in a somewhat simplistic fashion. A casual reader of the American press would believe, as the Arab diplomat did, that there is such a thing as an all-controlling Jewish lobby, that it always gets its way in Washington and that there is also something called the Jewish vote which, for reasons never quite explained, makes its vote really count -- maybe twice.

All this would be enough to make you believe in something called Super Jew. He votes with the power of two people and he raises money like three and spends it on political causes like four. When he comes to Washington, which is often, he makes his rounds of Congress, telling each and every member how to vote. Of course, they do as they are told.

Some of this is just a bit silly, not to mention insulting to Jews. It presupposes an incredible unity of thinking, a voting block that reacts to a single issue like the Rockettes at the Radio City Music Hall -- one-two, cast your vote.

There is no denying that an an ethnic group Jews have certain traits in common. They are, as a rule, better educated and more affluent and more liberal than the general population and, in my experience, prone to see bigotry in simple criticism. They tend to vote Democratic and they do tend to vote. But that is a long way from saying or predicting that they will all vote the same way because of a single issue, usually something having to do with Israel, frequently something not even considered basic.

This, though, is what the media seemed to expect. Jews, we are told, would punish President Carter for the snafu on the U.N. resolution by voting for Edward M. Kennedy. Florida, Illinois and New York is where Carter would be punished.

It hasn't happened. The best polling data in this case is not very good (the samples are too small), but in both Florida and Illinois it appears that Jews did not abandon the president in any wholesale manner. And in New York the polls show Jews sticking with Carter. In Florida, they did vote for Kennedy in greater numbers than the general population -- but not enough to make a difference.

In Illinois, Jews once again were a bit less enthusiastic about Carter than the general population, but it is hard to say that this is because of the U.N. resolution or because the Jewish vote, like Kennedy himself, is liberal. At any rate, Carter's pollster, Patrick Caddell, checked some of the heavily Jewish precincts in the Skokie area and detected no mass Jewish defection at all. He put it this way: "It's clear we commanded the Jewish vote."

This was not supposed to happen. Jews were going to go to Kennedy in great numbers. It was presumed for some reason that they did not also share qualms about Chappaquiddick and all it represents. It was assumed also that they agreed totally with the policies of the Begin government and did not give Carter any credit at all for his accomplishments at Camp David.

The result of this kind of thinking is that neither side is given its due. Carter is not so cynical as to construct a Middle Eastern policy for votes alone and Jews aren't so dazzled by Israel that a whole bunch of them don't have serious questions about the policies of the Begin government.

It's no wonder then that my Arab friend was mystified. He kept hearing and reading about someone called Super Jew, and when the voting was over, Super Jew was nowhere to be found. Maybe he once existed, but he sure does not exist now. Times have changed and so has he.

Maybe he's sitting out the election in Miami.