Ross Douthat gets it right:
what Nelson, Collins, Specter and Co. have done isn’t a new kind of politics. It’s the definition of politics as usual. And in this particular case, there’s a reasonable argument that it’s actively pernicious – that if you can’t shrink the stimulus package much more substantially than the centrists have done, you shouldn’t shrink it at all. There’s a case to be made for a stimulus that’s radically different than the one we have now; there’s a case to be made for a stimulus that’s like the one we have now, but a great deal smaller and more targeted; and there’s a case to be made for a stimulus that’s absolutely gargantuan. But thanks to the centrists, we’re getting the cheapskate version of the gargantuan version: They’ve done absolutely nothing to widen the terms of debate about what should go into the bill, and they’ve shaved off just enough money to reduce its effectiveness if Paul Krugman is right – but not nearly enough to make it fiscally prudent if the stimulus skeptics are right.
This means that if the damn thing doesn’t work, we won’t even know whom to blame. But it wouldn’t be crazy to start by blaming the centrists.