Representative Jim Clyburn of South Carolina explained this in visceral terms when he announced his support for Joe Biden late last month, an endorsement that began with Mr. Clyburn, 79, talking about the first time he was arrested protesting for civil rights decades ago. “When I sat in jail that day, I wondered whether we were doing the right thing, but I was never fearful for the future,” he said. “As I stand before you today I am fearful of the future of this country. I’m fearful for my daughters and their futures, and their children, and their children’s futures.”

Mr. Clyburn said he was sure Mr. Biden was the right choice. “I know Joe. We know Joe. But most importantly, Joe knows us,” he said. Three days later, Mr. Biden won a convincing victory in the South Carolina primary, launching him into his Super Tuesday triumph and the front-runner status he enjoys today.

My friends in New York, many of them Elizabeth Warren or Bernie Sanders supporters who see Mr. Biden as deeply uninspiring, were mystified. But after traveling through the South this past week, I began to understand. Through Southern eyes, this election is not about policy or personality. It’s about something much darker.

Not long ago, these Americans lived under violent, anti-democratic governments. Now, many there say they see in President Trump and his supporters the same hostility and zeal for authoritarianism that marked life under Jim Crow.