[I]f John Boehner has the courage of my convictions, he’ll believe that a government shutdown will risk sending the economy into a double-dip recession and that ultimately Barack Obama will be blamed for the bad results regardless of what polling says in the moment...To an extent, I think the functioning of our political system depends on the key actors not fully understanding how it works.I'm not sure that's correct, however. A two-to-four week shutdown of the government sometime between the beginning of the fiscal year in October 2011 and, say, January 2012 isn't, I don't think, especially likely to push the economy over the brink. A devious Speaker Boehner would be smarter just pushing for a Hooverite balanced budget -- a blend of middle-class tax increases and spending cuts guaranteed to lower aggregate demand, preferably in emergency legislation rushed through in late winter 2011. If Barack Obama vetoed, the GOP would be able to claim the moral high ground on deficits, with support of the scolds and schoolmarms on elite editorial pages; if he signed, well, that really would make a double-dip likely. Of course, it's not even remotely possible that House Republicans would do such a thing. (But if they were to propose it -- would they get Blue Dog votes so they could claim it was bipartisan? Could be!).
The thing is that if we're talking about a government shutdown, then what we're talking about is an inability to get appropriations bills signed into law by October 1 -- and an inability to agree to (routine) temporary measures to keep agencies funded while negotiations continue. The form this has to take is either Congress doesn't produce anything -- in which case they'll take the immediate blame -- or they produce something that Obama vetoes. It's not an easy trick for Congress to manage to pass something that is generally popular but so unacceptable to the Democrats that Obama would have to veto. In the case of a divided Congress, even if Democrats only hold a very slim margin in the Senate, I'd say it's just about impossible.
As far short-term fallout, I agree with Beaudrot that it's difficult to see a shutdown hurting Obama. Yes, within the GOP echo chamber, he'll obviously be blamed for it...but within that world, he's blamed for everything. But for everyone else, it's very hard for "Congress" to win any public relations battles. Everyone hates Congress; everyone always hates Congress. If government offices are closed, if national parks are closed...does anyone really believe that John Boehner is going to win a contest with Barack Obama in the battle for public opinion? Especially since reporters have been primed by the 1995-1996 confrontation to blame the incoming GOP Congress and not the Democratic president. Of course, this gets even easier for Obama if the stalemate is within Congress, with a Democratic Senate refusing to accept budget cuts pushed by a GOP House. And, really, is any pol better positioned to go on TV and play the above-it-all, willing-to-compromise president than Barack Obama? In sorrow and rather than in anger, he'll go before the cameras and say that he'd love to cut a deal but he just can't throw grandma out of her nursing home and close down Johnny's school...as we know, as unpopular as it is in the abstract, most federal spending is extremely popular when it comes to specifics, and it won't be hard for the White House to find all the tragic stories in any package of cuts.
Now, if the economy were derailed, it might be worth it for the reasons that Yglesias suggests -- at least for the Republicans, in the aggregate. For individual Members of the House, the calculations might be different, at least when looking to the general election. But, yes, an economic crash in 2011 would presumably help Republicans win the White House in 2012. However, as I said, it's a bit hard to see a the kind of shutdown that happened in 1995-1996 really having that effect.