It's hard to keep up with the twists and turns in this presidential race. Hillary Clinton under fire on Benghazi! Ben Carson has a theory about the pyramids! Bernie Sanders wrote about rape fantasies! Donald Trump . . . well, Donald Trump! Figuring out which headline will have the biggest impact on the general election is a bit of a parlor game. But what if they have no impact at all? After the 2012 election, political scientists John Sides and Lynn Vavreck wrote a book called"The Gamble"that looked at the cause of President Obama's victory over Mitt Romney. They sifted...