Sohn: Donald Trump is exposing the GOP's underbelly

Donald Trump, a Republican presidential hopeful, speaks at a campaign rally at the International Air Response hangar in Mesa, Ariz., Dec. 16, 2015. (Caitlin O'Hara/The New York Times)

Republican politicians have long used a political code-word playbook, and many of the code words involved the poor, women and minorities - especially racial minorities.

Mitt Romney liked to talk about the "entitlement society." Newt Gingrich used the "food stamp president."

"Lawless" and "thug" were favored insults directed at President Barack Obama by right-wing radio commentator Rush Limbaugh and others. "Thug" was also used to describe Trayvon Martin and outspoken Seattle Seahawks cornerback Richard Sherman. It was Sherman who noted that "thug" seemed to have become an "accepted way of calling somebody the N-word."

Ian Haney Lpez, a law professor at the University of California, Berkeley, in his book published last year, "Dog Whistle Politics: How Coded Racial Appeals Have Reinvented Racism and Wrecked the Middle Class," outlined how politicians and plutocrats attract white votes by deploying veiled racial messages that allow the speaker to deny any responsibility for the racial content of the message.

But