Few things make me more dizzy than arguing with conservative critics of the Affordable Care Act about Medicare. First they attack the bill for not doing enough to control Medicare costs. Then they attack the bill for doing too much to control Medicare costs. Often, they say these contradictor things at the same time, which makes you wonder how strongly they feel about either argument.

Of course, not all conservative critics of the Affordable Care Act are so cynical. Some, like David Brooks, seem genuinely concerned that the Act will not control the cost of Medicare. But these critics can be infuriating too, simply because they seem so unaware--or willfully ignorant--of the political dynamic at work here. Matthew Yglesias explains.

I’m happy to acknowledge that the steps ACA takes to restrain the growth in Medicare spending are modest. But “modest” is better than nothing. Some of us have also noted that Republican ACA opponents had a marked tendency to complain that ACA did too much to restrain the growth of Medicare. And of course if you repeal a bill that acts modestly to restrain the growth in Medicare spending, you increase the growth rate of Medicare spending. So some of us wonder why folks are sitting around complaining to liberals that we’re not enthusiastic enough about cutting Social Security spending instead of complaining to conservatives about their efforts to undermine the only legislative vehicle to restrain Medicare spending that’s on the table.