Post-terror nerves aside, what mainly ails the U.S. economy is too much of a good thing. During the bubble years businesses overspent on capital equipment; the resulting overhang of excess capacity is a drag on investment, and hence a drag on the economy as a whole.

In time this overhang will be worked off. Meanwhile, economic policy should encourage other spending to offset the temporary slump in business investment. Low interest rates, which promote spending on housing and other durable goods, are the main answer. But it seems inevitable that there will also be a fiscal stimulus package.

That package should include only measures that really will promote spending now, when the economy needs it. It shouldn't include anything that worsens the long-run budget position more than is necessary, or anything that looks like ''hitchhiking,'' exploiting the short-run difficulties of the economy to pursue unrelated long-run goals.

Unfortunately, the Bush administration has just taken a big step away from those principles.

Until late last week it looked as if much of any stimulus package would consist of increased government spending to rebuild New York, to pay for military operations and to provide unemployment benefits. This would put money into the economy in a clearly temporary way.