Nate Silver says Republicans ought to worry about the snowball effect:
[E]ach Republican lawmaker who comes out against the bill makes it a bit less popular — and that in turn increases the incentive for other Republicans to break ranks too. Some Republican House members might be willing to stomach voting for a bill that has the support of 45 percent of the voters in their districts, but if popular support is just 40 percent, or 35 percent, they may throw in the towel. So a feedback loop develops, and one defection begets another.
The Dish 