Jonathan Chait has a strong argument up today against my conclusion that John Boehner should avoid a shutdown. His best point, I think, is that while Boehner is in trouble regardless, at least if there's a shutdown he can say that he fought hard for conservative priorities. That's a fair point.
Still. Chait asks "What is the downside to cutting a deal? GOP backbenchers revolt against Boehner and depose him as Speaker of the House." But my argument is that at the end of the day, for better or worse, Boehner will eventually have to sign off on a deal. The question is, I suppose, whether he'll get more points for "fighting" -- or whether he'll be in more trouble because the longer the shutdown, the more high-profile it's going to be, and the less conservatives outside the House will be to look the other way and forget about it once it's over.
Not to mention that within the House the non-crazy part of the conference will have a lot less reason to support Boehner if he couldn't spare them from a budget disaster. One that, once it starts, may be very difficult to control.
In the event, it probably doesn't matter; odds are that Boehner doesn't really have much choice at this point, anyway.
At any rate, if you find my argument compelling, be sure to read Chait's different interpretation, since he may well be correct.