John Sides writes: Prognostications about the upcoming midterm election are coming fast and furious. The bullishness about the Democrats’ prospects, so frequently expressed (and exaggerated) during the government shutdown, is gone. Current forecasts typically range from “a midterm headache for Democrats” to possibly even another Republican wave. But at this moment, what’s most likely is something less dramatic, at least as far as the House of Representatives is concerned. An early version of this blog’s forecasting model suggests that there will be only a small shift in House seats in 2014 — one more likely to advantage Republicans than Democrats, but one that will fall far short of a wave.
The forecasting model, which political scientist Eric McGhee and I developed, is centered on what we might call the “fundamentals” of House elections. It is based on elections from 1952-2012. It takes advantage of key indicators at the national level: the popularity of the president as of June of the election year, growth or decline in the economy (gross domestic product) in the first two quarters of the election year, and whether it is a presidential or midterm election year. (Similar factors went into a presidential forecasting model that I helped develop for Wonkblog in 2012.) The model also builds in key indicators at the district level: the partisanship of the district as measured by the presidential vote, and whether a Democratic, Republican incumbent, or no incumbent is running in the district. Thus, the model provides a forecast not just of how many seats each party will have in the House as a whole, but of the outcome in each district. We first deployed this model in 2012, and it proved quite accurate.