THIS IS THE stage of the budget cycle when the leak becomes a weapon of choice. Decisions are still in flux. A disappointed agency or an ally on the outside will leak its budget to gin up opposition while time remains to change the president's mind. Or the administration itself may leak a tested decision to accustom the public to it, get some early credit, generate support or see how much flak it draws.

Some preliminary jockeying of this sort has begun with regard to the defense budget. The services received significant increases in the tight current budget year. They want further increases next year, without which they say they will have to cancel modernization plans. They are right that the dollars in prospect aren't enough to cover all the weapons on their wish lists. But that's a chronic condition for which at least two solutions exist: Increase the dollars or shrink the lists. Civilian officials say that after this year's increase the services ought to settle next year for the rate of inflation--a break-even budget--but that's not where the fight is headed.

There is maneuvering in the area of agriculture as well, another source of the budget breakout in the appropriations cycle just ended. In each of the past two years, Congress has voted large "emergency" agriculture appropriations that allowed it to provide farmers with generous support while pretending to stick to the system of minimal support that it proudly adopted as a reform in 1996. The administration has egged it on, even while deploring the emergency bills as poorly conceived. Next year--election year--the same script is likely to be followed. Both sides are busily positioning themselves to get maximum credit for granting the extra aid but minimum blame for breaching the budget.

A third major battle is building over aviation aid, an increase in which was stymied this year. The advocates will be back.

A game is being played at a higher level as well. Both parties are pledging once again not to use the Social Security surplus to finance the rest of government. Any election-year tax cut or spending increase will have to be financed out of the prospective surplus in other than Social Security funds, they say. But the surplus in other than Social Security funds will materialize only if they adhere to appropriations caps, which imply deep spending cuts that neither party is prepared to vote for, nor should be.

Each party is trapped by its position in this dance. When the president proposes to spend more than the caps, the Republicans accuse him of advocating spending increases--reverting to tax and spend--even though he is merely fending off cuts. But he can't say he is merely averting unacceptable cuts, because to do that would be to renounce the caps, which in theory he supports.

His tactic instead is to propose that the spending be financed by devices like a cigarette tax increase, which he knows they reject. He then attacks them for refusing to approve the spending anyway, and they relent. The caps are breached, but in a way that makes it hard to say that either party did it, a series of fictions that allows them both to have the thing both ways. What they ought to do is agree to raise the caps, but then there wouldn't be any non-Social Security surplus to spend, and what would be the fun of that?