As he says, it makes no sense — unless you consider the possibility that the anti-deficit lobby doesn’t really care about deficits. If you believe that its real agenda (not always consciously) is to dismantle the welfare state, with deficit fears as the excuse, then the seemingly bizarre positioning makes perfect sense. Democrats trying to preserve the essence of the New Deal and the Great Society are always deemed insufficiently committed, never mind the numbers, while Republicans eager to tear the whole thing down are serious people, never mind their obsession with budget-busting tax cuts.
I don't really agree with that. Krugman is describing the views of conservative Republicans who posture as opponents of the deficit. But the anti-deficit lobby is a different group with different beliefs and positions. They oppose deficit-financed tax cuts as well as social spending.
None of this is to say I agree with the perspective of the anti-deficit lobby, but my differences are much narrower than my differences with movement conservatism. I think members of the anti-deficit lobby are genuinely committed to the concept of "non-partisanship," defined in such a way that they frequently cannot interpret reality. Well, that and they believe they need to maintain a posture of non-partisanship in order to keep their credibility.
Even on that score, I notice that the Washington Post today editorially pats Obama on the back. They'll be back to pox-on-both-houses-ism soon enough, but it is worth noting the distinctly different tone today.