Statistician and FiveThirtyEight founder Nate Silver famously used “big data” and his mathematical models to predict all 50 state outcomes in the 2012 general election, somehow besting his mark of 49 during the 2008 cycle. The one he got wrong that year: Indiana, which went to Barack Obama by a 0.1 percent margin. For all the numbers and polls and graphs that likely passed Silver’s desk in the weeks prior to that November, the famed prognosticator needed only to focus on a 403-square mile plot of land along the road between Indianapolis and St. Louis. There, the roughly 108,000 citizens...