All this brings to mind a young presidential candidate named Barack Obama, who warned in 2008 that Republicans would play the race card. “They’re going to try to make you afraid of me. ‘He’s young and inexperienced and he’s got a funny name. And did I mention he’s black?’” he told a rally. Mr. Obama won, and won again, but that hasn’t stopped Democrats from rolling out that same racism charge at any opportunity, using it in particular as a tool to drive minority turnout in elections.

Such racial exploitation is possible because the two U.S. political parties are so divided along racial lines. The appeal wouldn’t work if Republicans took 40% of the black vote, instead of the 10% or less they get in the Obama era. For that the GOP is partly responsible for not trying harder.

But Democrats do themselves no credit and the country no good by playing up racial divisions for partisan ends. Alas, they’ll keep doing it until voters stop rewarding them with votes.