Given the vocal opposition to the bill, why would Kagen still vote for it? Well liberal blogger Matthew Yglesias offers this:
The point is, for a first cut at predicting legislator behavior you should look at their partisan affiliation, not the views of their constituents. Beyond party affiliation, there is evidence that constituent public opinion makes a different. But legislators have a fair amount of leeway.He's convinced that party affiliation is a good proxy for voting record and that the actual wishes of constituents matter, but maybe not as much as we all would like to think. Yglesias doesn't believe this is a good thing, but it is an observable tendency.
I think he usually bemoans this phenomenon when conservative Democrats refuse to support the Obama/Pelosi legislative agenda citing concerns back home or when Republicans don't support legislation that opinion polling suggests is popular among some part of the electorate.
This habit of bucking the wishes of constituents for the concern of the party can have a way to come back to haunt a candidate, especially a marginal Democrat like Kagen. This is the kind of vote that Pelosi usually would give a pass on, but I think this one was too close for that.
It remains to be seen if this will hurt Kagen in 2010. If even a portion of the feelings from August remain, I don't see how it can't.