The political story of the week is the stunning defeat of House majority leader Eric Cantor in Virginia’s seventh district. Nobody predicted that Cantor would lose to a no-name, Tea Party-backed economics professor -- least of all, Cantor’s pollster, John McLaughlin. Less than a week before the election, McLaughlin forecasted that Cantor would win by 34 percentage points. Instead, he lost by ten. How did the pollster get it so wrong?