Why it's impossible to predict this election

The bottom line is that in a bizarre election like this one — with so many variables and so much emotion — polls may well under- or over-predict votes for the two major candidates. Think about the vote on Brexit. Virtually all the polls — including exit polls that asked voters how they voted — got it wrong. The financial markets got it wrong. The bookies got it wrong. The 2016 presidential election is more like the Brexit vote in many ways than it is like prior presidential elections. Both Brexit and this presidential election involve raw emotion, populism, anger, nationalism, class division, and other factors that distort accuracy in polling. So those who think they know who will be the next president of the United States are deceiving themselves.

One reason for this unique unpredictability is the unique unpredictability of Donald Trump himself. No one really knows what he will say or do between now and the election. His position on important issues may change. Live televised debates will not allow him to rely on a teleprompter, as he largely did in his acceptance speech or in his speech during his visit to Mexico City. He may once again become a loose cannon. This may gain him votes, or it may lose him votes. Just remember: Few, if any, pundits accurately predicted how far Trump would get when he first entered the race. When it comes to Trump, the science of polling seems inadequate to the task…

A final reason why this election is so unpredictable is that the voter turnout is unpredictable. The “Bernie or bust” crowd is threatening to stay home or vote for the Green Party. Young voters may do here what they did in Great Britain: Many failed to vote in the Brexit referendum and then regretted their inaction when it became clear that if they had voted in the same proportion as older voters, Brexit would likely have been defeated. Some Clinton supporters worry that black voters who voted in large numbers for Barack Obama may cast fewer votes for Clinton in this election. Voters who usually vote Republican but can’t bring themselves to pull the lever for Trump may decide to stay home. The effect of low voter turnout is as unpredictable as turnout overall.