As Dave Weigel points out, it's not really a few dozen crazy Republicans provoking the government shutdown. It's Republican primary voters all across America. They hate Obamacare and they're willing to defeat anybody who doesn't take a sufficiently hard line against it, just like they've been defeating a long line of electable Republicans in Senate primaries.
Ted Cruz may be the star of the movement, but his role was to bring a particular extreme political option within the scope of Tea Party hopes and dreams so that the Republican base would pressure their legislators to pursue it, not to build a coalition of legislators by himself on Capitol Hill. That's what I'm liking about him -- he strengthened the force that's tearing the Republican Party apart, and it should help Democrats win more legislative races next year, as it did in the last two cycles. One hopes that these forces don't tear apart the country, but assuming that we can pass budgets and debt ceiling increases, the majoritarian structures of democracy provide protection against that.