Sam Wang Says the Polls Give Harry Reid a More than 50% Chance of Being Senate Majority Leader Next January...: Live from The Roasterie CCCXX: September 1, 2014
Sam Wang: Senate Democrats Are Outperforming Expectations: "The PEC Senate poll snapshot is more favorable to Democrats than...
...The Upshot... The Monkey Cage... FiveThirtyEight, and Daily Kos.... Today’s PEC snapshot... favors the Democrats with a 70% probability.... The major media organizations (NYT, WaPo, 538)... all use prior conditions like incumbency, candidate experience, funding, and the generic Congressional ballot... and opinion polls.... The first data column is the current PEC poll median. The next two columns show what a polls-only win probability looks like. Finally, the last three columns show the media organizations.... Democratic candidates in the nine states above are doing better in the polls-only estimate than the mainstream media models would predict.... Why is that, and will it last?
For PEC and Daily Kos, the win probability is closely linked to the poll margin.... The mainstream media organizations are a different story.... Longtime readers of PEC will not be surprised to know that I think the media organizations are making a mistake. It is nearly Labor Day. By now, we have tons of polling data. Even the stalest poll is a more direct measurement of opinion than an indirect fundamentals-based measure....
DailyKos, the Upshot, and FiveThirtyEight have win probabilities are closer to 50% than PEC’s in 18 out of 27 cases... trying to predict November races on an individual basis... drags their total expectations toward randomness.... The Monkey Cage, which shows higher certainty than PEC in 6 out of 9 races--but sometimes in the opposite direction. This suggests that their model must be heavily weighted toward fundamentals. That is very brave.... [Using the] Meta-Margin, and the t-distribution with 3 d.f., to predict the future, including the possibility of black-swan events... [gives a] November Senate win probability for the Democrats (i.e. probability that they will control 50 or more seats) is 65%.... Note that this is all a work in progress...
