The Time for Change Model once again correctly predicted the winner of the US presidential election. In late August, before the Republican and Democratic national conventions, the model predicted that President Obama would win 50.6% of the major party vote to 49.4% for his Republican challenger, Mitt Romney. When all the votes are counted, it now appears that Obama will end up with approximately 51.8% of the vote, making the Time for Change Model one of the nation's most accurate statistical forecasting models. Despite the fact that this prediction was made more than two months before Election Day, the Time for Change forecast was more accurate than the results of many national polls conducted immediately before the election including the Gallup and Rasmussen tracking polls both of which predicted a popular vote win for Mitt Romney.

The Time for Change Model has correctly predicted the winner of the popular vote in every presidential election since 1988. This year, however, I made one small modification to the model. In addition to the three predictors that I have used since 1988—the incumbent president's net approval rating in late June, the change in real GDP during the second quarter of the election year, and a dummy variable for first-term incumbents, I added a polarization correction for elections since 1996. The polarization correction reflects the reduced willingness of voters to cross party lines to vote for an incumbent from the opposing party or any candidate from the opposing party in an era of heightened partisan polarization. Thus, the incumbency advantage enjoyed by President Obama was estimated to be about half the size of the advantage enjoyed by first-term incumbents before 1996.

The results of the 2012 presidential election provide strong support for the inclusion of the polarization correction. According to the national exit poll, the level of partisan voting in 2012 was the highest since the beginning of presidential exit polls in 1972—92% of Democrats and 93% of Republicans voted for their party's candidate. The result was a close election in which the modest-6-point Democratic advantage in party identification proved decisive.

It now appears that President Obama will exceed his predicted share of the major party vote by just over one percentage point. Part of this error may be attributed to the fact that economic conditions in the United States continued to improve somewhat during these two months with unemployment falling below 8% shortly before the election. Perhaps more importantly, the president's approval rating on Election Day was somewhat higher than it had been in late August. According to the data from the national exit poll, Obama had an approval rating of 54% with a disapproval rating of 45%, yielding a net approval rating of +9% compared with a net approval rating of +2% in the Gallup Poll at the end of June. Nevertheless, an error of approximately one percentage point is certainly acceptable given the forecast's lead time of more than two months.

As they search for explanations for their party's defeat this year, Republicans can at least look forward to the 2016 presidential election with some hope—after eight years of Democratic control of the White House, the time for change factor will swing back in favor the GOP.