Many Republicans in both chambers of Congress (e.g. Speaker Boehner) have publicly said they oppose Robamcare and its funding, but not at this price. A clean continuing resolution would sail through the House with significant Republican and near unanimous Dem support—which is exactly why ~50 Tea Partiers forbid a vote. That idiotic Hastert rule lets them effectively filibuster within their own party; it is an informal Republican rule and perhaps sufficient cause in itself for a Democratic House majority.

So Tea Partiers can and do threaten fratricidal primary challenges if any fellow Republicans dare resist them. In many cases that would hand Dems otherwise safe GOP seats by nominating unelectable extremists (Dick Lugar was unbeatable in last years general election, but when Republicans replaced him with Richard "rape is Gods will" Mourdock Dems won a Senate seat in a state Romney won by 10%.) Even when it did not many GOP incumbents would lose their jobs regardless.

Frankly, I would be loving this did it not menace my country. Republicans have no visible means to save their election chances next year: They doom themselves by prolonging the shutdown (especially if it extends to a disastrous federal bankruptcy) OR by caving in and prompting the Tea Partys retaliation by nominating unelectable extremists to replace GOP incumbents. I personally think half the reason things have strung out this far is because Boehner and Co. are hoping that if they wait long enough Obama will tell Dems to cave as he always has (small chance of that; he deems Robamacare his legacy, probably accurately) or some other miracle will save them. But "hope" in one hand and crap in the other and see which fills faster.

Democrats know it, too; one of yesterdays stories was about Dems noting the GOPs position, and thus leverage, just gets worse the longer this continues, and therefore hoping it continues until the upcoming debt ceiling vote so Republicans have no option but complete capitulation. That is a fine idea except for one thing: What if the stakes grow so high the GOP decides it CANNOT blink? Federal bankruptcy, and disaster.