Princeton Election Consortium

A first draft of electoral history. Since 2004

VP guessing (part 2) and electronic markets

August 27th, 2008, 2:48pm by Sam Wang

The Meta-Analysis EV estimator is unlikely to move much until post-convention polls come in. It appears that the post-houses gaffe cost John McCain 15 EV. We probably won’t ever know the exact amplitude, but I’m guessing it’s at least that much.

My first VP guess (Sebelius or Kaine) wasn’t so good. This time I’ll use actual data for the GOP pick…

Mitt Romney. My guess is based on electronic markets, which correctly named Joe Biden as the favorite. Now InTrade says Romney.

Update, Thursday, 9:45pm: Wow, there’s a bidding boomlet for Gov. Pawlenty, whose share price was a distant second until today. Maybe not Romney after all?

In general, electronic markets monitor the wisdom of crowds. One benchmark is Presidential races, where they folllow polls fairly well; see the current standings at They lag polls a bit and express much less certainty than polls, even on Election Eve. Both phenomena may account for why the current standings there are Obama by 37 EV, half the margin reported here.

In a sense, the reduced certainty reflects the possibility that swings may happen in the future. As you can see in this graph of InTrade prices versus polling margins, they usually get the sign right. But even a 10-point margin isn’t enough to saturate bidder confidence:

InTrade prices vs state polls

InTrade prices vs state polls

I find InTrade state-race probabilities useful as a benchmark to see how good they are. Let’s see how they do for the Republican VP pick.

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One Comment so far ↓

  • chaunceyatrest

    My decidedly unscientific prediction for McCain’s VP is Pawlenty. He’ll appeal to the fundamentalist base of the party, he’ll dial the average age of the ticket down to something like 149, he’ll allow McCain to continue with the fiction that he’s interested in bipartisan cooperation, and he’ll increase McCain’s chances of flipping MN — which, if I’m not mistaken, is within the MOE in the most recent polls. Anyhoo, we’ll know soon enough. Chatter around the inter-webs suggests that McCain will try to steal Obama’s acceptance speech thunder by announcing his pick this evening.