From the Washington Post, quoting E.J. Dionne:

He added that a key to understanding why the party has been so split by Trump’s candidacy is what conservative intellectuals have been noting all year. “The Republican Party relied for decades on white, working-class voters and delivered no material benefits to them,” Dionne said. “Oddly, a man who says he is a billionaire has become the avatar of a working-class rebellion inside the Republican Party.”

https://www.washingtonpost.com/politics/a-party-that-doesnt-recognize-itself-convenes-in-cleveland/2016/07/15/0a057adc-4490-11e6-88d0-6adee48be8bc_story.html?tid=pm_politics_pop_b

The same could be said of the Democrats.