>Or is the logic here as simple as "if blowup, vote for non-incumbent"?
I suspect the logic amongst the Tea Party crowd may well be that, given enough disinformation, people will follow that logic. Certainly the driving logic behind Fox News is that, if you can claim that everyone else has a bias and nobody tells the truth, then one man's truth is as good as another's. The Tea Partiers can claim that this is Obama's fault and do what Boehner did after Obama's speech: obfuscate and obscure with half-truths and red herrings.
I suspect that a good chunk of the Tea Party crowd would be willing to accept the economic disaster that could result from this brinkmanship, if it meant they could rebuild according to their goals and beliefs. The Tea Partiers are activists in every sense of the word. Primarily, that means that they believe the current system is hopelessly broken, and that it needs to be fundamentally dismantled and rebuilt. As in any revolution, a period of chaos is to be expected, and even celebrated, as it represents the death throes of the old order.
The Republican mainstream won't let that happen. They'll agree to the closure of modest tax holes in exchange for deeper cuts, and the debt ceiling will be raised. As much as they complain about government spending, the Republican mainstream are Old Order politicians, just like their Democrat counterparts. Boehner just needs to ride a fine enough line to appease the Tea Partiers and so carry their support into 2012, which is the only reason I can think of that he's acting the way he is.