Proxy Models and Nowcasting: U.S. Presidential Elections in the Future

Election forecasting as a field of political science has come of age, doing so with a roar during the 2012 U.S. presidential election contest. The more established approaches are digging deep, while the less established approaches are giving them a good challenge. The synergy has moved the science of election forecasting, not to say the public attention to election forecasting, to a new plane. There are multiple approaches, and the number continues to increase. The leading ones are still opinion polls, trading markets, and statistical models. (For a full contemporary account of such strategies, see the symposium by Lewis-Beck and Stegmaier [2014a].) With respect to statistical models, two basic strategies have emerged: state-level modeling and national-level modeling. Our work follows the latter strategy, and during the 2012 U.S. presidential election campaign we developed proxy models, using them as nowcasts to predict the contest. In brief, our proxy model sought to forecast the 2012 national result as a function of an empirical surrogate variable of the vote itself. Starting one year before the election, we updated our prediction each month, in a nowcast regularly released on The Monkey Cage, the blog site (http://www.washingtonpost.com/blogs/monkey-cage/). Our final proxy model nowcast, appearing well before the election, and based on data gathered six months before, predicted the election almost exactly at 52.7% (versus the actual 52.0 popular two-party vote share for Obama). In the article at hand, we begin with discussion of how different forecasting approaches fared, when trying to predict the 2012 U.S. presidential election. Next we develop the proxy model idea, drawing on our earlier examples from other democracies, before applying it to U.S. presidential elections. Once explained, we submit the proxy model for these U.S. elections to various diagnostics, including the out-of-sample forecast of the 2012 contest. Given certain attractions of the proxy model, we attempt to account for why it works. Then, we explore its use in nowcasting, again drawing on our earlier nowcasting work, before testing it against the 2012 election. By way of conclusion, we offer an evaluation of proxy model performance along four traditional criteria--accuracy, lead, parsimony, reproducibility and--a new one--currency. By these standards, the proxy model seems, perhaps deceptively, a simple solution to the complex task of forecasting U.S. presidential elections. Different Forecasting Approaches: Accuracy in 2012 In the study of U.S. election forecasting, there are different approaches. Several contemporary reviews of this material have appeared (Lewis-Beck and Tien 2011; Lewis-Beck and Stegmaier 2014b; Stegmaier and Norpoth 2013). Setting aside the identification of clever "coincidences" that seem to predict presidential election outcomes, such as how well the Redskins do, or how good the current Beaujolais harvest tastes, there are a variety of more solid approaches, occupying a different place on the scientific continuum. (On "coincidences," see Lewis-Beck and Rice 1992, chap. 2.) With respect to the continuum, at one end are studies of predictive "keys" to election success and the naming of special "bellwether" counties or states that seem to track the presidential outcome such has been alleged most recently for Ohio. (On "keys" and "bellwethers," see Nadeau and Lewis-Beck 2012.) At the other end of the spectrum are opinion polls, political trading markets, and statistical models, which represent the bulk of the scientific election forecasting enterprise. Opinion polling organizations led, at least until recently, by the Gallup organization, have long provided vote intention surveys that are widely used to predict election outcomes. Many current rivals to Gallup exist, foremostly perhaps Pew for individual surveys and Real Clear Politics for aggregations of these surveys. Political trading markets are mostly represented by Intrade and the Iowa Electronic Market, although the former appears to be dropping out of the game. …