In the last century, no major-party presidential candidate has ever endorsed violence (George Wallace did in 1968, but he was a third-party candidate). Trump broke this pattern. During the campaign, Trump not only tolerated violence among his supporters but at times appeared to revel in it. In a radical break with established norms of civility, Trump embraced—and even encouraged—supporters who physically assaulted protesters. He offered to pay the legal fees of a supporter who sucker-punched and threatened to kill a protester at a rally in Fayetteville, North Carolina.
