Trump Remarks on Harris Evoke a Haunting and Unsettling History

White America has long sought to define racial categories — and who can belong to them. The audience of Black journalists was prepared for a combative exchange well before Donald J. Trump took the stage on Wednesday for an interview at their annual gathering in Chicago. Yet when Mr. Trump, just minutes in, began questioning Vice President Kamala Harris’s racial identity, there was an instant ripple of reaction — a low rumble that grew into a roar of disapproval. “I didn’t know she was Black until a number of years ago when she happened to turn Black and now she wants to be known as Black. So I don’t know, is she Indian or is she Black?” Mr. Trump said of Ms. Harris, whose mother was Indian American and whose father is Black. The moment was shocking, but for those who have followed Mr. Trump’s divisive language, it was hardly surprising. The former president has a history of using race to pit groups of Americans against one another, amplifying a strain of racial politics that has risen as a generation of Black politicians has ascended. The audacity of Mr. Trump, a white man, questioning how much a Black woman truly...