THE BUSH administration has shifted not just its position on taxes but its role in the budget debate. The president spent his campaign and first year and a half in office doing just what the Reagan administration had done before him: using fanciful projections to minimize the deficit. Now he has apparently decided to begin to address the fiscal danger rather than continue to duck it. To goad the summit negotiators and resisters in both parties in Congress, he and his aides have turned to emphasizing how large and intractable the deficit is.

In January his projection was that the deficit, absent any further steps to reduce it, would be about $100 billion in the next fiscal year, already comfortably down from slightly more than $120 billion expected this year. Now the projections have shot up to $161 billion this year and $168.8 billion next. If you count the currently estimated cost of bailing out the savings and loan industry, the figure for next year rises to $231 billion. If you strip away the masking effect of the Social Security surplus, it rises to more than $300 billion.

It's a little hard for the president and his budget director to explain how the figures got so much higher in just six months, but no matter. What they're saying now is what a president and budget director ought to be saying in the current circumstances. As with national security, so with economic: better to err, if you err at all, on the conservative side of foreseeing too much risk rather than too little. The new truth-telling makes all the more anomalous the balanced budget amendment to the Constitution on which the House is scheduled to vote today, and which, sadly, the administration still supports.

This is not what its title promises. It would not outlaw deficits, but merely make them harder to amass by requiring three-fifths votes of both houses both to overspend revenue estimates in any given year and, as a second line of defense, to borrow in order to cover such overspending. But if Congress failed to abide by its terms, or evaded them, what would anyone do? Take Congress to court and have the courts become fiscal arbiters? This is a fig leaf in a situation that requires political courage. Nor is it economically wise to enshrine one kind of fiscal policy in the Constitution. The House should vote no. The place to solve the deficit problem is at the summit, not in the Constitution.