Call it the curse of high expectations. When Barack Obama took office, the world swooned, America exhaled and pundits declared an end to centuries of racial division. Gazing at the 1.5m people who braved the cold to witness Mr Obama’s inauguration, Steven Spielberg said it would have been impossible to stage for a movie. That was then. Today America’s first non-white president is winding down at the nation’s tensest moment of racial polarisation in decades. Thanks to Donald Trump, the Ku Klux Klan is back in the headlines. I doubt Mr Trump will succeed Mr Obama as president but he has injected poison into the bloodstream. For all Mr Obama’s hopes, fear is the dominant currency.

Much like the end-of-history declarations in the 1990s, America’s racial history did not end with Mr Obama’s election. It simply opened a new chapter. Nations, it seems, suffer from similar disorders to humans — what happens in their formative years shapes their character for evermore. Just as India sees foreign investors as potential colonisers, and Britain confuses Brussels with the papacy, so the US is enchained to its original sin of slavery. Half a millennium after the first Africans were shipped across the Atlantic, the US still has one foot in its past.

Do not take my word for it. Listen to Mr Trump’s supporters. According to exit polls in South Carolina, which Mr Trump won handily last month, a fifth of those who voted for him thought that Abraham Lincoln was wrong to emancipate slaves. Just over a third wished the south had won the civil war. Ted Cruz, who looks like Mr Trump’s only viable rival, had similar numbers. Seventy per cent wished that the Confederate flag was still flying above the state’s capitol building. It was removed last year following the massacre of nine black churchgoers by a self-declared confederate. “The past is never dead”, said William Faulkner. “It is not even past.”