The attack on the defense budget has begun, and suddenly this city is like a small room with a large stereo system playing a peculiar record. Arguments that for years have been pouring from the speaker on the left have been adjusted a bit and are pouring from the speaker on the right.

For years liberals have said: we favor a "strong defense program," but we mean by that a "reformed"military, "lean" and purged from "waste," with much procurement postponsed until after a "strategic debate." Besides, the key to military strength is not military procurements. Rather, the key is urban revewal and affirmative action and a high minimum wage and . . . the entire liberal agenda. Why? Because only a happy, egalitarian, equitable American can be harmonious at home and a stunning example to the contested Third World.

Now, even as the president commits himself to such strategic systems as the MX missile and the B1 bomber, some conservatives are saying: we favor a strong defense program, but we mean a reformed military, lean and purged of waste, with procurement postponed until after a strategic debate. Besides, the key to military strength is not military procurements. Rather, the key is a balanced budget, a smaller percent of GNP for government, relaxation of the Clean Air Act, drilling in wilderness areas, and . . . the entire conservative agenda. Why? Because only an economically vigorous American can be militarily strong.

The conservative rationalization, unlike the liberal rationalization, concludes with a truism. However, both are rationalizations for not doing what is unpleasant but necessary. And implicit in the conservative argument is the assumption that the U.S. economoy cannot match the Soviet buildup.

The Soviet economy is much smaller, and is a tissue of irrationalities. Yet the Soviets spend 85 percent more than the United States on procurement. Americans spend (it sometimes seems) 85 percent of their time and energy concocting reasons why military material is not a necessary response.

These are crises in Poland, in the Persian Gulf and in Central America, but the deadly crisis in Kansas. I pick that state at random. It is moderate, humane, patriotic, and it favors increased defense spending -- until that spending interferes with balancing the budget. And it favors a tough foreign policy -- stopping short of grain embargoes, naturally.

A similar analysis would fit any of the 49 other states. Will a tough foreign policy play in Peoria? Up to a point -- the point at which the government, looking for ways of expressing disapproval of the proposed Soviet-to-Germany gas pipeline, considers blocking sale of pipe-laying machines made in Peoria by the Caterpiller Corp.

Many Republicans seem to fear the government in Washington more than the government in Moscow. They say: "The Soviets can't even build good tractors. Why worry?" The answer is: if a war between us is fought with tractors, we win. And if it isn't perhaps we can bombard them with copies of the federal budget, prettily bound and nicely balanced.

The Soviet Union is losing every race except the one we dare not let it win: the arms race. Remember, the Third Reich, far from being a materpiece of Teutonic efficiency, was a jungle of bureaucratic feudalisms. But it could organize a mighty army.

The modest ($13 billion over three years) cuts the president has proposed for his defense program are not important for their size but for the principle they express. They legitimize treating the defense budget as a target of opportunity in the scramble for scarce resources. As a result, Congress may triple his proposed cuts. A carefully nurtured and terribly fragile consensus in favor of rearmament is being dissipated by an administration that seems to be saying: rearmament is important -- but less important than other goals.

The president is more trustworthy than his party regarding a strong foreign policy. The GOP has long been the home of isolationist impulses, some of which remain. In fact, some Republican enthusiasm for big strategic systems like MX is related to that impulse. Such systems suggest a comforting capacity for dealing with the world at a distance; they allow the nation to think it car be exempt from involvement in dirty details of what John Kennedy called "the long twilight struggle."

Imagine how perplexed Moscow's ideologists must be when they see American headlines proclaiming: "Stock Market Plunges Wall Street Calls Defense Cuts Too Small.' Such headlines are awkward for those who say that militarism is all that sustains capitalism. These are hard times for those in the Kremlin whose job it is to make communist explanations fit American behavior.