Perhaps most disturbing of all, just 29 percent of Americans as a whole think race relations are getting better, while 32 percent think race relations are getting worse. The difference is too close to call, but the fact that it is so close is itself painful — and perhaps a warning sign for where we are heading.

Is this what so many Americans, both black and white, struggled for, over the decades and generations, to try to put the curse of racism behind us — only to reach a point where retrogression in race relations now seems at least equally likely as progress?

What went wrong? Perhaps no single factor can be blamed for all the things that went wrong. Insurgent movements of all sorts, in countries around the world, have for centuries soured in the aftermath of their own success. “The revolution betrayed” is a theme that goes back at least as far as 18th century France.