ELECTION LAB POST-MORTEM

SY M P O S I U M Evaluations of the 2014 Midterm Election Forecasts James E. Campbell , University at Buff alo , SUNY , guest editor L ike wines, for election forecasting there are some good years and then there are some not so good years. The 2014 vintage of PS election forecasts, now aged past runoff s and recounts, ranks among the more successful of years. In the October 2014 issue of PS , fi ve forecasters or teams of forecasters published their predictions of the 2014 midterm congressional elections. Each predicted partisan seat changes in the US House and three of the fi ve also predicted seat changes in the US Senate. Each of the forecasts was made at the end of August, between 9 and 12 weeks before Election Day. With the 114th Congress now sworn into offi ce, it is time to step back and evaluate how well the forecasts performed. In this re-cap, the forecasters off er their evaluations of their predictions. Before reviewing the performance of each of the individual models, however, a few thoughts about the general performance in 2014 of the PS forecasts are in order. First, as a group, the House forecasts were quite accurate. Republicans gained 13 seats in the House. Their majority increased from 234 following the 2012 election to 247 members in the new Congress. Because their numbers for a Republican majority were already high, making gains more diffi cult, this outcome could be characterized as a wave (or mini-wave) election for Republicans—and the forecasters pretty well caught the wave. The median forecast predicted Republicans to gain 14 seats, only one seat off . Four of the fi ve forecasts were within three seats of the outcome. Although chance has some small role in this degree of accuracy, especially with many races being decided by razor- thin margins, the fact that most of the forecasts were so close to the actual outcome should count to the forecasters’ credit. Second, making this accuracy of the House forecasts more impressive is that these were not “safe” forecasts. Four of the fi ve forecasts predicted double-digit seat changes in an era in which these are not the norm. Net partisan seat swings had been held to fewer than 10 seats in 10 of the 14 national elections held since 1986. The political landscape of 2014 also suggested a small seat swing. The 2012 election left very few split-result districts, districts in which opposite parties won presidential and House vote pluralities. These are the districts one would look to for change, and there were precious few of them. Finally, in predicting Republicans to gain more than eight seats, the forecasts were predicting that the Republican Party would emerge from the election with a larger majority doi:10.1017/S1049096514002327 than it had after the 2010 landslide midterm (242 seats) and its largest majority since the one sent to Washington after Herbert Hoover’s defeat of Al Smith in 1928. This was not an easy election to forecast, and these were not cautious forecasts— and they were made nearly three months before the election. Third, the accuracy of the Senate forecasts, in general, is more diffi cult to characterize. With Democrats defending 21 of the 36 seats up for election, with fi ve of those being open-seat contests, and six having been carried in 2012 by Mitt Romney by at least 14 points, Republicans were positioned for sub- stantial seat gains. The question was how substantial? Would Republicans gain the six seats required for them to control the Senate? Two of the three Senate forecasts (Abramowitz and Highton, McGhee, and Sides) saw this as essentially a toss-up. One (my forecast) predicted an eight-seat Republican gain with better than two to one odds of Republicans capturing a major- ity. With the Louisiana runoff completed, Republicans gained nine seats in the election. Considering how close many of the races were and the long lead time of the forecasts, this was a respectable-to-very-good showing for these forecasts. Finally, the PS forecasts compared quite favorably to other forecasts, most notably the relatively new crop of forecasts that have sprung up in media outlets over the last several election cycles. The PS forecasts are more transparent (the specifi cations are clear and public), have longer lead times before the election, are more stable (eschewing frequent or even daily updating), and are generally more parsimonious and uncomplicated. Moreover, the forecasts possess these many virtues without apparently sac- rifi cing anything in terms of accuracy–if 2014 is any indication. The comparisons are clearest in the 2014 Senate forecasts. Although each eventually predicted a Republican Senate majority, in mid-September of 2014 (more than three weeks after the PS forecasts were made) Nate Silver’s “538,” the New York Times’ “Leo,” and the Washington Post ’s “Election Lab” (updating Highton, McGhee, and Sides’ PS forecast) cast the Senate majority as a toss-up. Sam Wang’s Princeton Election Consortium at the time had the Democrats heavily favored. The PS forecasts were at least as accurate or more accurate than these media forecasts—moreover, they achieved this accuracy earlier and without the noise created by the fl urry of incessantly updated forecasts. While there is much to celebrate here for the PS fore- casts, one election is but one election, and each forecasting © American Political Science Association, 2015 PS • April 2015 295