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August 17, 2010


Good point, Brendan. Sounds like Silver is trying to boast that what he's working on will be better than the overall average approach, and he denigrated that approach too much.

Silver's main assertion is that the generic ballot is not a good predictor of national seat results. It would be interesting to see a chart like the one above testing that assertion. That looks tricky to me. One would have to consider the generic ballot as of various points in time.

Also, past generic ballots may have used different methods, which may not be directly comparable to today's methodology. Presumably the "generic ballot" means the RCP average or something like it. Past generic ballots may not have been tallied or may have used averages of different polls.


I think the other thing to keep in mind is that, reading Nate Silver's post, I think he conflated two things, but what he really seems to be talking about is how well the generic ballot can do in helping predict the results of the 435 individual races. It can do quite well to predict the overall disposition of the chamber, assuming the generic ballot accurately predicts the national vote share, but it's indeed quite possible that it's relatively irrelevant to the results of any particular district, other factors considered

But where is the generic ballot at today? Rasmussen has Republicans up by 8. Gallup has the generic ballot tied. And the rest of the pollsters fall everywhere in between. That seems like a huge range to me. Is this kind of scatter normal for these polls? Or is 2010 unusual.

Sorry, I just don't see it.

Looking at the pdf from 2006, there's only an .83 correlation between generic vote and actual vote. And then there's only a .93 correlation between actual vote and seats taken.

That's what, a .77 correlation from generic vote to seats taken as a base? There has to be a better indicator than that.

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