DID YOU EVER really doubt it? The White House now acknowledges that the budget deficit is back on a track that, despite all of this summer's struggles with spending cuts, will produce $200 billion deficits next year and the year after. It's as though the deficit were on a spring. Wherever the estimates and forecasts begin, as time passes they eventually snap back to $200 billion.

It's a pattern that has been repeated annually for the past four years. The latest cycle, over the past six months, began with the president's budget last February. It called for a deficit of $180 billion next year, an improvement over the current figure. Then, six months later, after a mighty struggle, Congress got it down to $172 billion. That was a week ago. Now the Office of Management and Budget warns the president that the true figure is still in the range of $200 billion after all.

The spending cuts -- most of them, at any rate -- are not fake. The chief source of the slippage is in the economic forecasts. Last February the budget- makers, as is their habit, took a highly optimistic view of economic growth in 1986. Currently the evidence indicates a much less rapid expansion -- meaning lower tax revenues. A more precise assessment is to appear at midweek, when the Congressional Budget Office expects to publish its own revisions. The White House says that it also expects some upward revision of the deficit with appropriations bills that overstep the limits Congress has just set in its budget resolution. That's certainly possible. But the implication -- that the deficits result from congressional refusal to follow the president's budget proposals -- is incorrect.

White House staff people say that they want to see a budget next winter that will push the deficit down over the next three years from 4 percent of GNP to 3 percent to 2 percent. Those are useful targets, but they are the same targets that the White House staff tried to put in place a year ago. It turned out that Mr. Reagan was unwilling to make the choices required even to meet those goals on paper -- even with those very optimistic assumptions about the economy. And now, six months later, even the president's deficit projections are being revised upward again.

The point of all this highly repetitive experience is that a dangerously large structural deficit is not going to be remedied by the kind of marginal fiddling around to which Mr. Reagan has limited himself since 1982. It's going to take something more serious. Like what? Like -- to say it once more -- a tax increase.