This seems to be moving fast, and it will be interesting to see if it keeps happening. I'm sure the corporate interests in the Chamber that support inaction on climate aren't persuaded by any of this, but other corporations that hadn't cared much before might want to start thinking about their own self interest, as the Chamber starts losing significant political and financial capital.
The Chamber's response is a smokescreen statement pretending they'd support a treaty that would somehow get 60 votes in the Senate and that would also force "each nation" in the developing world, no matter how poor and how tiny its per-capita greenhouse gas emission is, into binding reductions. What would be much more interesting than this nonsense is to know what the internal discussions are saying. Time for business journalists to get on it.
As for environmental strategy, I think in the short term at least this incipient crisis for the Chamber supports a quitting strategy over the "stay and fight" strategy I've advocated. Maybe a merger of the two strategies would be for environmentally-oriented businesses to start turning around local and state chapters, though. Another would be for BICEP or a similar group to organize more broadly as a business alternative to the US Chamber, something that might truly scare it.