Friday, November 19, 2010

Checking Nancy Pelosi's Math

On Tuesday, during a marathon meeting of the Democratic caucus of the United States House of Representatives, Nancy Pelosi made the following argument to her colleagues...It was the economy that did in the Democrats in the recent midterm elections. It wasn't her fault that the party suffered such a historic loss of seats.

What evidence did Pelosi cite in defense of this argument? One element of her claim was that pre-election forecasting models predicted that Democrats would lose in the vicinity of the 61 seats that ended up switching over to Republicans. These models, she told her colleagues, derived such predictions largely from the fact that the economy is struggling mightily, a factor that is historically associated with steep electoral losses for the party in the majority.

Wondering whether Pelosi's claim holds water, I took a quick look at some of the forecasting models that political scientists produced prior to Election Day. As it turns out, there certainly were some models that forecasted Democratic losses in the range of 50 seats. These models, however, tend to incorporate factors other than, or above and beyond, the state of the economy. Such factors include the generic ballot, in which likely voters are asked whether they will vote Democratic or Republican in their congressional election.

As for those models that most heavily weight the economy, the typical prediction was in the 25-30 range in terms of Democratic seat loss. What these models in combination suggest is that, based solely on the sad state of the economy, 2010 definitely shaped up as a bad year to run as a Democrat. That said, the best guess of the economy-based forecasting models was that Democratic losses should have been much smaller than how things actually turned out, small enough in fact that Democrats stood a reasonable chance of retaining their House majority.

What, then, explains the "excess" loss of somewhere in the vicinity of 30 Democratic seats? Can responsibility for these losses be laid at the feet of party leaders such as Nancy Pelosi? Although that is too big of an inferential leap to make from the models themselves, what can be clearly stated is that Pelosi's argument doesn't withstand empirical scrutiny of pre-election political science forecasts. It was not just the economy that was at work earlier this month in upsetting the balance of power here in DC. Exactly just what was it then? That's, of course, what Democratic and Republican strategists will desperately be seeking to figure out between now and Election Day 2012.


PS: Click on this link for the figure that accompanies this post, as well as for many more details about the 2010 political science congressional election forecasts.


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