Spread evenly, the cuts would come to more than 20 percent in each broad category. Cuts that deep in a single year have occurred only once, from 2009 to 2010, when the temporary increase from the stimulus reverted to more normal levels. Otherwise they are unprecedented, and no wonder. A 20 percent cut in education, for instance, would take some $8 billion out of federal money for schools, deepening the teacher layoffs and other cutbacks already enacted by states.

And for what? Cutting any arbitrary amount — like $100 billion — from discretionary spending will not result in meaningful long-term deficit reduction because deficits are not driven by discretionary spending. They are driven by rising health care costs and chronic tax shortfalls. Such cuts are even unlikely to result in near-term deficit reduction, because lawmakers would have to vote each year to keep spending at the newly depressed levels, an unlikely — and undesirable — prospect.