At the beginning of August, the University of Iowa did a rather interesting poll. They asked Democrats and Republicans who they were supporting in the primaries, and showed how the numbers progressed under a series of increasingly tight screens. Shown below are the numbers for the 469 registered Democrats, the 425 Democrats who didn't rule out going to the caucus, and the 319 Democrats most likely to go to the caucus:
As likelihood of caucus attendance increases, so does support for Edwards (and Richardson). This isn't surprising -- the highly interested voters who go to caucuses pay attention to candidates outside the spotlight. Obama's sweet spot seems to be among the middle category of probable caucusgoers, while Hillary's support slides as you get closer and closer to the caucusgoing population. (For reasons unknown to me, RealClearPolitics continues to display the results with 425 respondents, despite the fact that the pollsters say that sample is "not directly comparable to the March UI Poll sample of likely caucus goers.")
