The Horse Race: What Polls Reveal as the Election Campaign Unfolds

The horse race of election campaigns is of great interest to scholars of public opinion and the public itself (Iyengar, Norpoth, & Hahn, 2004). In almost every democratic country, pollsters regularly ask samples of the public about their choices in the next election. The practice now is so common in some countries that hardly a day passes during the official campaign without encountering results of new polls, often from multiple organizations. In these so-called trial-heat polls, citizens typically are asked about how they would vote ‘if the election were held tomorrow.’ Although we now have many polls, they give only imperfect readings of electoral preferences—poll results consist of true preferences plus survey error. Part of the error is simple sampling error, which is well-known. There also is error owing to the different methodologies that different survey organizations employ, however. Results may differ across survey houses due to differences in weighting samples, screening for likely voters, and other practices (see Groves, 1989). The effects not only are real, they may have increased over time (see Wlezien & Erikson, 2001). Given evident differences across survey houses, how can we trace the evolution of electoral preferences during an election campaign? How can we tell whether and how the horse race changes as the election campaign unfolds before us?