Nate Silver on the Senate Post 2010

While Nate Silver, the man behind the poll analysis site FiveThirtyEight, is quite liberal in his personal beliefs he manages to do a decent job not letting that bias influence his statistical approach to making sense of polls. This morning he has an interesting article where he tries to predict the makeup of the Senate after the 2010 elections.

The whole thing is worth a read. He breaks down each race state by state and considers the possible candidates (and where appropriate races where one opponent is still unknown). The part I want to quote, however, is from the beginning.


Right now, the program is showing that Democrats will retain an average of 54.7 seats in the 112th Congress. The distribution, however, is slightly asymmetrical, so the median number is 54, and the modal number is 53.

And things could, potentially, get a whole lot worse than that; the program recognizes that the outcome of the different races are correlated based on changes in the national environment. Between the surprise in Massachusetts, and races like California and Indiana which are potentially coming into play, there’s about a 6-7 percent chance that Republicans could actually take control of the Senate, and another 6 percent chance or so that they could wind up with a 50-50 split. On the other hand, there’s still a 7-8 percent chance that the Democrats could regain their 60th seat if the national environment shifts back in their direction.

Emphasis mine. I think that’s pretty remarkable. While almost every pundit on either side of the aisle has predicted gains for the Republican party in the Senate, the idea of gaining control was typically considered a pipe dream. While a 12-13% chance is still a small chance, it is much higher than I would have assumed.

To reiterate, Silver tries to keep his politics out of his analysis. His Monte Carlo based approach proved to be accurate during the 2008 election cycle. Yes, he does always phrase things in terms of a seat going Republican as a “loss” and to a Democrat a “gain”. But for our hyper-partisan readers, I’ll suggest you try to get past that. His analyses are often a good read for poll junkies like myself.

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