The Republicans controlled Congress and the White House for six years; they could have made government as lean as they wished and no one could have stopped them. They didn't. It used to be that when they proposed irresponsible or phantasmagoric tax cuts, Republicans at least went through the motions of coming up with some theory about how they would pay for themselves. Supply-side economics--tax cuts would generate new taxable economic activity--often played this role. It made no sense, but it honored the tradition of giving voters the material they need to fool themselves. That was the tribute demagoguery paid to mathematics. Now, Republicans don't even bother.
What's especially disheartening is that one of the leading proponents of repealing the AMT without offsetting it with new revenue or spending cuts is none other than Chuck Grassley. As Eve Fairbanks noted last month, whatever other problems liberals had with him, he was at least somewhat honest on matters of fiscal policy. If even Grassley has drunk the budgetary Kool-Aid, that's not a good sign.
Kinsley is also right to point out that aside from raising needed revenue, the AMT makes a good deal of sense from an economic standpoint:
Actually, if you were designing the tax system from scratch, you might come up with something that looks a lot like the AMT. It resembles the "flat tax" of many reformers' dreams: a high basic exemption, so that low-income people don't pay it at all; very few deductions, credits or exclusions; and (because of that) a much lower top rate than the current system: 26%, compared with almost 40%. Of the two parallel tax systems we have--the regular income tax and the alternative minimum tax--it might make more sense to scrap the regular one and keep the AMT.