When Sen. Rand Paul launched his presidential campaign, he promised to be a Republican who wouldn't just support criminal-justice reform as a policy platform (as some other presidential candidates, including New Jersey Gov. Chris Christie and Sen. Ted Cruz, have) but talk openly about mass incarceration and the war on drugs as racial issues. He was supposed to be running to reach out to non-traditional Republican constituencies: young voters and African Americans. During most of the campaign, that Paul hasn't been much in evidence. Over the summer, when he has talked about race, he's sounded more like a typical Republican:...