Last fall, when William F. Weld was running for governor of Massachusetts, he used a simple analogy to explain how easy it would be to cut the state budget. It would be, he said, "like squeezing water from cheese." Nothing important would be lost. The product would be just as good.

In those same weeks, David Walters was telling the voters of Oklahoma what they might expect from him if he won the governorship. "We are going to change Oklahoma," he vowed. There would be substantial commitments to funding the 1990 education reform law, improving the correctional system, rehabilitating prisoners with new programs in literacy and vocational training. The money would be there: In a $6 billion state budget, a competent administrator should be able to find $100 million right away by stamping out inefficiency.Just how many voters believed those assertions is impossible to say. Presumably millions of them did, because Republican Weld and Democrat Walters were both elected. In a gubernatorial campaign, it still pays to talk of funding an ambitious set of commitments painlessly, without new taxes or drastic service cuts, through the simple expedient of making government more efficient.

Waste, fraud and abuse are the Loch Ness monster of American politics. Candidates keep insisting they have seen it, and if given a chance, they will prove that it exists. The fact that they never produce much evidence of it after the election only seems to give the legend more credence with every passing election year.

People who have watched a few rounds of this won't be surprised at what has happened in Massachusetts and Oklahoma this year. Walters did manage to provide about $3 million in new money for prisoner rehabilitation, but not by any magic streamlining process. His budget took painful hits at the Departments of Health, Mental Health and Veterans Affairs, and at the programs they operate. The "water" that Weld proposed to squeeze out of the Massachusetts "cheese" turned into severe cutbacks in health programs and support for the elderly and a sharp reduction in aid to localities.

Any new governor has the right to make substantial spending cuts at a time of budget austerity, and health departments and local aid programs all over the country no doubt contain their share of trimmable fat. What is depressing is the whole political sequence: the continued willingness of politicians to pretend that there are no hard choices involved, the eagerness of the voters to believe them and the absence of any mass outcry when, just a few weeks after the election, the process generates exactly the kind of pain that the newly installed leaders insisted it wouldn't.

The difference between the limitless promises of fall and the austerity of late winter is, of course, the difference between campaigning and governing. Governing is choosing among competing goods, deciding to honor some of the items on one's wish list and putting others aside.

Deciding which dreams to fulfill and which ones to delay or abandon isn't a simple matter of administrative competence, as candidates like Walters and Weld like to insist. It is a painful process in which many people get hurt and some people feel betrayed.

Do cynical politicians brainwash the innocent, well-meaning voter with empty promises? Or do voters generate the promises by rewarding those who make them and punishing candidates who dare to talk openly of trade-offs and sacrifices?

Maybe a little of both. It seems safe to predict that as soon as the voters start refusing to support candidates who try to sell them the Brooklyn Bridge, nobody will be out there selling it.