September 11, 2008 | Mother JonesEmory political science professor Alan Abramowitz seems to have a mathematical election model that works. Abramowitz's system has correctly predicted the popular vote winner within two percentage points for every presidential election since 1988. The model isn't perfect, of course, but it does factor in a wide range of variables such as GDP, a party's time in office, and recent polls. If you're skeptical of models, check out the IOWA ELECTRONIC MARKETS trading index for the presidential election. For decades, it's been a much better predictor of presidential wins than Gallup polls.