THE CONSERVATIVE MOVEMENT IS GOING TO EMERGE FROM A GOVERNMENT SHUTDOWN AT LEAST AS POWERFUL AND EVEN NASTIER
I know I'm supposed to believe that shutting down the government is going to be a disaster for the Republican Party -- respectable (i.e., non-Rasmussen) polls make clear that the public will blame the GOP, and even mainstream Republicans recognize the risks -- but I don't think it's going to do any serious harm to the conservative movement.
One obvious reason is that groups such as the Club for Growth, Heritage Action, and the Senate Conservatives Fund are using this moment to fund-raise like crazy. This is the money that's going to bankroll Republican campaigns in 2014 and 2016.
But beyond that is the fact that even a terrible hit for the GOP in the 2014 elections will probably not reduce Republican extremism at all. Democrats need a gain of 17 seats in the House to regain the majority. Even in 1998, the much-mocked, Gingrich-led, impeachment-mad House GOP lost only five seats. And a government shutdown before the 1996 election led to GOP losses in the House of only two seats. Are Dems going to win an extra 17? Not when we're reading that, because of gerrymandering and clustering of voters, Democrats would need to win the overall House vote by a 13-point margin in order to accomplish that, according to Alan Abramowitz of Larry Sabato's Crystal Ball. (Right now, no pollster thinks Democrats are even close to that on the "generic ballot" question.)
So the House is almost certainly going to stay Republican. And the Senate? As long as the GOP maintains at least a 41-vote superminority (the GOP has 45 seats now, and is more likely to gain seats than lose any), it can filibuster its way to a stranglehold on any legislation.
And remember, there might be fewer Republicans in the next Congress, but there are going to be more crazy Republicans. This situation is raising big bucks for the groups that are going to back crazy primary challengers for "establishment" Republicans. And since most GOP seats, in the House and the Senate, will stay GOP no matter who wins the primaries, that's going to up the crazy quotient even if it decreases GOP numbers slightly.
So the result of what's going to look like a debacle for the GOP will be a shot of testosterone for the party's crazy wing. And since the party will have approximately as much power in the next Congress as it does now, total wingnuttery in Congress will actually increase. Thus, shutting down the government is a perfectly rational strategy for the barking-lutanic wing of the GOP.
UPDATE: DougJ beat me to this.