Some are subjective, but this is interesting.
http://www.theamericanconservative.com/articles/unlocking-the-election/
http://www.theamericanconservative.com/articles/unlocking-the-election/
We can never know what the electorate will do until it goes to the polls and unlocks the secret of its collective sentiment. But some political scientists have sought to parse the referendum concept through analytical frameworks that lay bare the essence of voters’ presidential decisionmaking. Of these, the most compelling was put forth by Allan J. Lichtman and Ken DeCell in their 1990 book, The 13 Keys to the Presidency. Lichtman and DeCell reject the notion that the electorate renders its presidential decisions based upon such things as negative ads, clever slogans, fund-raising disparities, campaign gaffes, or big-name endorsements. They believe, rather, that the voters, exercising their collective franchise, bring sound judgment to the task of choosing their leaders, that their decisions are based on big-picture considerations and not trivia, and that the country’s referendum guidance system has remained consistent through the country’s presidential history.