That New York Gov. Mario Cuomo is as personally intelligent as he is publicly eloquent is obvious to nearly every national political reporter who has covered the man. Cuomo is reflective, witty and practically unbeatable in New York, where Republicans are having considerable difficulty finding anyone willing to run against him next year.

Why, then, a reasonable person might ask, would Mario Cuomo, who had publicly and repeatedly urged fellow Queens Democrat Geraldine Ferraro to run for the Senate in 1986, make the announcement that was in Monday's New York Post? When asked whether he was prepared to help Ferraro should she run, Cuomo said: "I'm going to be very busy with a campaign of my own." On Wednesday Ferrraro announced she would not run aginst Republican incumbent Alfonse D'Amato.

What we have here is a continuing pattern of political pettiness on the part of Mario Cuomo. Remember "polenta"? That's the Italian version of Cream of Wheat, a bland mush, to which Cuomo in December 1983 compared his endorsed presidential candidate, Walter Mondale. While the press smiled at Cuomo's witticism (which he had cutely attributed to his mother, Immaculata), the Mondale people grumbled about his perfidy. But even the grumblers had to acknowledge the value of the governor's all-out support for Mondale's victory in the New York primary.

But then in October of last year, just a couple of weeks before the presidential election, there was Mario Cuomo publicly ruminating in The New York Times about whether he, himself, would run for president in 1988. It was widely assumed that Mondale, if he were to win, would seek a second term. So here was his principal New York backer simply writing off Mondale. More grumbling from the Mondale folks, but most of us in the press, enchanted by Cuomo's eloquence and wit and depth, paid little attention and attributed the grumbling to charisma envy.

By now the circumstantial evidence must be stronger than the breath of a buffalo. Yes, Mario Cuomo can inspire by reminding us that "a society as blessed as ours should be able to find room at the table, shelter for the homeless, work for the idle." And, yes, Cuomo is regularly capable of gratuitous acts of political pettiness. As one Mondale lieutenant put it right after the "polenta" affair: Cuomo could be that rare politician who recklessly enjoys embarrassing political allies to their political disadvantage even though no political advantage is thereby conferred upon him.

If the Democrats are to regain control of the Senate in 1986, it almost certainly means that D'Amato must be beaten. Ferraro was one Democrat with the fund- raising capacity to compete with D'Amato's campaign war chest of more than 5.5 million, even though she trailed the incumbent in a recent survey, one that also gave Cuomo a job rating slightly higher than Santa Claus's.