Via Twitter, Garrett Jones challenged me to revisit out dispute from back in June about the explanatory power of the median voter theorem. He seems to feel that Olympia Snowe’s vote in favor of health reform offers strong support for his position.
To which I say . . . sure, Snowe’s vote is a reminder that public opinion has some bearing on legislator behavior. Nevertheless, I would just repeat my initial points. Richard Burr and Kay Hagan have the exact same constituents, but different views on health care. Same with Chuck Grassley and Tom Harkin. Look at every state represented by senators from different parties. Insofar as the median voter theorem has explanatory power, we would expect those senators to be pulled toward the same position on health care. But that’s happening in either zero of those states or else only in Nebraska. Or consider the public option dispute among Democrats. Webb and Warner are listed with different views, so are Dorgan & Conrad, and Dodd & Lieberman.
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.