Does the upcoming election mean it's time to reassess your portfolio? A historical look at presidential elections & the stock market can help you decide. A simple stock market metric has correctly predicted the winner in 20 of the last 23 presidential elections since 1936 — a track record that might make even the top pollsters jealous. If the S&P 500 Index is up in the three months prior to Election Day, the incumbent party usually wins. If markets are down during that period, the opposing party typically claims victory.