“I would like to place a large wager against that guy…” says @NateSilver538 of @SamWangPhD‘s projection, which heavily favors Dems. — Brian Lehrer Show (@BrianLehrer) September 8, 2014



I guess when you’re the King of the Nerds, you have to be willing to engage in a little trash talk. I think this is a good time to administer a lesson in probability* – and also question who is doing the “heavy favoring” around here. [*see postscript – Sam]

The PEC Election Day prediction indicates a 70% probability of Democratic+Independent control. That is based on polls alone, plus the assumption that September-October will act like June-August. FiveThirtyEight’s probability is 64% favoring the Republicans, based on a model with polls plus a substantial dose of special sauce (a.k.a. fundamentals).

I guess it is a good time to make a bet, if you are the kind of guy who makes a lot of bets. Personally, I am conservative about these things. It seems best to hold one’s tongue until an outcome gets into 90% territory. In my analysis, the pure polling data suggest that Democrats are favored. But to me, a wager at this time sounds like taking turns playing Russian roulette – for both players.

However, I do see a fairly juicy bet in the FiveThirtyEight calculation.

I have to say, this special sauce is messy stuff. Really, the GOP has an 25% chance (3-1 odds) of getting 54 or more seats? I’d put it at more like 5%. Even 53 GOP seats is a fairly outside outcome. If a betting person were offered the chance to put up $3000 against Nate Silver’s $1000 on that outcome…that would be taking his money.

Joking aside, there are two serious points to be made here. First, nobody should be getting excited about any probability that is in the 20-80% range. That includes Nate Silver, who knows better. Second, the addition of “fundamentals” and other factors adds considerable uncertainty to the projection.

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In other news, the Meta-Margin has dropped to D+0.9%, mainly because of a YouGov/NYT poll in Alaska that puts Dan Sullivan (R) ahead. Alaska is a problem for any poll-based modeler. However, the Meta-Margin is right at the middle of the range predicted by the polls-only model. As always, we must wait for more data.