Four weeks out from the election, and for most Americans, it’s time for football, foliage and flannel. For politics watchers, all eyes are on an October surprise.They’ve been game-changers before. In 2008, the collapse of Lehman Brothers, which ushered in the biggest financial crisis since the Great Depression, was a turning point in John McCain’s presidential campaign. He was even with Barack Obama when the news broke, then trailed in every survey after. He lost the popular vote by seven points.Surprises have come from home and abroad. In 1980, it was President Jimmy Carter’s inability to res...