Cleveland is shopping for riot gear. As the host of the Republican National Convention in July, the city has solicited bids for 2,000 sets of "Elite Defender" police riot suits, 26-inch collapsible batons, and thousands of interlocking steel barricades. That equipment may get heavy use if Republican leaders succeed in their desperate plan to wrest the presidential nomination away from Donald Trump at a contested convention. A contested convention promises to be, let us say, colorful, given the atmosphere at Trump rallies: Black and Muslim protesters are routinely pushed around, kicked, and dragged away with the full encouragement of Trump, who says that such "disgusting" people deserve to be taken away "on stretchers." If Trump is denied the nomination in Cleveland, a Trump aide warned this week, his supporters "will burn the place down." Any further questions?

Even if Trump wins the nomination outright, Peter Beinart pointed out last week at The Atlantic, our country "is headed toward a confrontation the likes of which it has not seen since 1968." The prospect of an authoritarian race-baiter in the White House will stir up real panic, and the raucous rallies of white, working-class Trumpists in every state will draw equally energetic protests from Hispanics, Black Lives Matter activists, and young leftists. What then? Katie Packer has an inkling. A Republican strategist who heads a super PAC devoted to stopping Trump, Packer is inundated every day with dozens of emailed and tweeted threats to kill her, her family, and her dog — "the most hateful vitriol that I've ever encountered in 25 years of politics." Trump, Packer says, has liberated people who "used to feel like they needed to keep quiet because what they say isn't acceptable in polite society." The months to come will be fascinating, dramatic, and historic. But they won't be polite, and they won't be pretty.