Still, the agitprop version of this week — that Reagan opened his campaign with an appeal to racism — is a distortion, as honest investigators ranging from Bruce Bartlett, who worked for the Reagan administration and is the author of “Impostor: How George W. Bush Bankrupted America and Betrayed the Reagan Legacy,” to Kevin Drum, who writes for Washington Monthly, have concluded.

But still the slur spreads. It’s spread by people who, before making one of the most heinous charges imaginable, couldn’t even take 10 minutes to look at the evidence. It posits that there was a master conspiracy to play on the alleged Klan-like prejudices of American voters, when there is no evidence of that conspiracy. And, of course, in a partisan age there are always people eager to believe this stuff.