Persuading poor people to vote against their economic interests is how the GOP wins. It’s scary how good they are at it…

The One Number That Will Decide This Year’s Election

For the past decade, the working-class vote has determined whether the country swung toward Democrats or Republicans.
MOLLY BALLJUL 24 2014, 12:30 PM ET

What will be the deciding factor in this year’s elections? Will it be Obamacare? The chaos erupting across the globe? The president’s approval rating? Will it be single women voters, Hispanics, young people?

Mike Podhorzer crunched the numbers and found there’s one factor that, with eerie consistency, explains the way elections have swung for the past decade. Podhorzer, the political director of the AFL-CIO, is one of the top electoral strategists on the left. The crucial factor, he found, is Democrats’ vote share among voters making less than $50,000.

Republicans consistently win voters making $50,000 or more, approximately the U.S. median income. The margin doesn’t vary too much: In 2012, Mitt Romney got 53 percent of this…