What happens to the budget now? The two congressional budget committees bravely announce that they will proceed at once to create order out of chaos. But it's not likely that they can change much without President Reagan's active cooperation, and Mr. Reagan doesn't seem to be in a conciliatory mood. In his budget address last week, he talked as though the sole reason for the soaring budget deficit were merely a stubborn refusal by the Democrats to cut spending. "They want more and more spending, and more and more taxes," he said.

In fact, last year Congress obediently passed the administration's two great bills, the budget cut and the tax cut, very much as Mr. Reagan wanted them. The budget cut was large, but the tax cut was much larger, and it will keep increasing over the next four years as its successive stages take effect. That disparity frightened people in the financial markets, and high interest rates aggravated the recession that began--in violation of supply-side theory--just about the time those bills were being passed last summer. With the drop in incomes and the rise in unemployment, the deficit has grown wider.

Mr. Reagan offers a solution: Congress must cut spending, as his budget proposes. But his cuts are small, compared with the looming deficit. All the budget's spending cuts together add up only to $29.6 billion. That figure, incidentally, takes at face value things like the vague references to prevention of waste, and it includes some decidedly unattractive items--for example, more big whacks at food stamps and the children's nutrition program.

The administration now tacitly accepts the congressional warning that the budget is on a track that, without further policy changes, will produce a deficit of about $180 billion next year. Even if Congress were to enact every cut in the president's budget precisely as the president proposed it, that would bring the deficit down to perhaps $150 billion --two and a half times the size of the deficit that Mr. Reagan inherited from Mr. Carter.

The president is using the Democrats as a surrogate for the more serious challenge that is coming from fiscal conservatives appalled at the prospect of running for reelection under the shadow of the biggest deficit since World War II. People in Congress realize that the president is running out of ideas for further budget cuts.

In his exasperation, Mr. Reagan has now embraced more warmly than ever a dangerously misguided idea --the constitutional amendment requiring a balanced budget. But a constitutional amendment won't make bad choices any better. If the only reason for the deficit is a recalcitrant Congress, as Mr. Reagan claims, why didn't his budget at least show Congress how to balance it? Why didn't he specify the broad deletions that could produce a balance?

The answer is, obviously, that the White House senses a lack of support, even in its own party, for any further substantial reductions. The successive rounds of cuts last year seem to have brought the budget pretty close to most Americans' idea of the basic definition of federal responsibility. If that is true, the only question worth discussing is the tax increase to pay for it.