A PREVIEW of the coming attractions of next week's budget reconciliation floor debate will be provided in the next day or two when the Food Stamp Bill is expected to find its way to the Senate floor. While the bill will also meet the requirements of the budget resolution, food stamps will come up first for a separate debate because the legislation is due to expire.

The bill that has emerged from the Senate Agriculture Committee would cut food stamp benefits by almost $1.9 billion next year, $400 million more than the administration requested. If the bill passes as is, millions of poor people will suffer significant losses in purchasing power, most of them elderly, disabled or in families with children.This is not a happy prospect-- but it could have been a lot worse. The committee did not adopt the administration's proposal to cut benefits to families with children receiving free school lunches, a plan particularly harmful to some of the nation's very poorest families. Instead it spread the losses more evenly by delaying cost-of-living increases, adding more administrative restrictions and reducing benefits to the working poor.

Having lost in his earlier attempts to achieve yet more massive reductions, Senate Agriculture Committee Chairman Jesse Helms is expected to be pushing some of his pet proposals on the floor. These include restoring the requirement that people buy their stamps -- formerly a major source of administrative abuse and a barrier to participation among the elderly and rural poor--further reducing income limits and cutting benefits across the board. The full Senate should reject these proposals, as did the Agriculture Committee.

Perhaps that is all that can be expected in the present climate. There is, however, one other matter that the Senate should address. That is ending once and for all the silly game now played once a year or more over the spending cap added to the Food Stamp Law in 1977. Each round of the game starts with a guess as to what the program is going to cost over the next few years. The guess is always lower than anyone really believes is necessary to serve all eligible people. Liberals go along with the underestimate in order to get agreement on the money needed immediately to run the program. Conservatives insist on the underestimate so as to have another chance to rail about a "runaway program" and offer restrictive amendments when, again, as the result of rising inflation or unemployment, program costs bump up against the ceiling.

The Agriculture Committee bill keeps this game going. The cap for this year has been raised at administration request by $500 million above the amount originally requested so that it is realistic in terms of the certainties of the near future. The limits for the next fiscal year and beyond remain at the roseate levels set earlier. Not only are these based on a highly optimistic forecast, but they make no allowance for the increase in food stamp cost--estimated at more than $500 million by the CBO--that will be caused by cutbacks in welfare, CETA, unemployment and trade adjustment assistance and other programs.

Whatever the attraction of familiar amusements, this is one game that Congress should decline to play anymore. If there is any safety-net program in this country, it is surely food stamps, the only program that serves all the poor and provides access to the most basic of all market commodities--food.