Dan Drezner asks why Republicans are ignoring business interests’ opposition to a shutdown:

Second, given the Chamber of Commerce’s tilt, why aren’t GOP representatives listening more closely? Presumably, this is a group that, if alienated, could actually choose to spread their money around more liberally.

I think Drezner’s second question is at least partly answered by the figures he cited earlier in the post. Because the Chamber of Commerce leans so heavily towards the GOP, Republican politicians may conclude that they can ignore some of its complaints without provoking the group to shift more of its support to the other party. Consistently and overwhelmingly favoring one party over another signals to party leaders that your group’s concerns can be dismissed more easily when the leaders have other priorities. The Chamber’s support for Republicans is being taken for granted because that support is so lopsided in the GOP’s favor, and as a result it sometimes has much less influence with what the party does in Congress than one would expect. Obviously, there are limits to how often and how completely a party can neglect its reliable supporters, but as long as a group is so heavily committed to one side it will be taken for granted by the party it supports and written off by the other as unreachable.

As for why business interests are siding so strongly with the GOP, it is important to remember that many of these business interests perceive Obama as almost uniquely antagonistic to them. This is very exaggerated, but the idea took root early on that Obama is ideologically driven to be hostile to business interests, and so many of those interests have lined up behind the Republicans in response to that perceived hostility. Indeed, the Senate races where the Chamber spent heavily in unsuccessful attempts to defeat Democratic candidates suggest that the main goal was to block the election (or re-election) of more economically populist Senators such as Brown and Warren. That tells me that Chamber of Commerce is more concerned with treating Democrats as their ideological enemy rather than seeking to influence them. That is why it has been throwing so much money at the Republicans, and it is probably also why Republican politicians feel confident that they can ignore the group’s objections to their losing shutdown strategy.