The lesson of 2018 is that the political class is addicted to drawing lessons. Every two years, after the ballots are counted and the winners declared, our reporters, pundits, officials, activists, and analysts turn immediately to the next election. What do these results portend? Will Trump be reelected? Will the suburbs stay Democratic? This emphasis on the future allows the political class to indulge in its favorite activity: mindless speculation. For once, it might be more useful to look backward rather than forward. History has much to tell us.