Nate, Daniel, and I write:
Lawmakers' support for or opposition to reform generally has less to do with the views of their constituents and more to do with the issue of presidential popularity. . . .
For instance, Senator Blanche Lincoln, a Democrat who has been a less-than-strong supporter of the present health care bill, recently told The Times, "I am responsible to the people of Arkansas, and that is where I will take my direction." But where does she look for her cue? Hers is a poor state whose voters support health care subsidies six percentage points more than the national average. On the other hand, Mr. Obama got just 40 percent of the vote there. . . ..
Public opinion is certainly relevant to the health care debate, but not in the direct senator-follows-the-state way that it is sometimes imagined.
Further discussion (including pretty maps) here.