If asked, most people would say that Nate Silver had the most accurate prediction of the 2012 election, but that’s not true. Silver actually mis-predicted at least one Senate race. It was Sam Wang who was perfect in 2012. Wang is a neuroscientist at Princeton University and the head of the Princeton Election Consortium. He was one of the first people to aggregate election polling, starting back in 2004. And he currently gives the Democrats a 70% chance of holding onto the Senate.
This came as a bit of a shock to me. I’ve been following 538, The Upshot, and The Monkey Cage models, and they all are very bullish on the Republicans taking control of the Senate. For example, The Upshot currently gives the Republicans a 65% chance. So what is going on?
The difference in the predictions is based upon the kind of models. Wang’s model is based entirely on polling data. As far as I know, The Monkey Cage is based entirely on fundamentals like the state of the economy. The Upshot and 538 models are a combination of the two. The truth is that the fundamentals suck for the Democrats. But as Wang noted today:
Of course, all of this could change. But the truth is that the election isn’t that far away: just over two months. One would think that if things were going to turn, they would have done so by now. But we haven’t seen any indication of that. But I know that I what to believe Wang’s results. Regardless, even his 70% Democratic probability result finds the most likely Senate makeup to be 50-50. The polls with the fundamentals have the Republicans controlling it 51-49. So the models are not all that different. It just shows that there is a lot of uncertainty. At this point, it doesn’t make much sense to get too excited or too depressed.
Update (29 August 2014 4:24 pm)
I just checked, and The Monkey Page model that a month or two ago had the Senate going Republican with an 80% chance, now gives the Republicans only a 53% chance. FiveThirtyEight can’t seem to be bothered to update their model more than once a month. Daily Kos gives Republicans a 55% chance. It is only The Upshot that gives the Republicans a big chance: 65%. That’s interesting.