As a companion to Terrence's post below, let me throw open a question: is it realistic to believe that we can return to genuine federalism?
Many people seem to assume that it's a hopeless case to try to restrict the federal government to it's enumerated powers because we'd have to get rid of so many "popular" federal programs. But why does that have to be? Why not just turn unconstitutional federal programs into voluntary programs that states can opt into -- or not. If medicaid, for example, is so popular, then presumably most states would opt in. Same with federal highways, social security, etc. Granted, there'd have to be some sort of grandfathering provision so that people in the "opt out" states get some return on the taxes they've been paying, but political pressure should take of that.