Libertarians, to the extent we can ever hope for real political success, should be excited about Rand Paul. But Paul, the Kentucky senator who is running for president, has treated his libertarian inheritance as more burden than boon. He's even called libertarianism an "albatross," though a growing, and young, share of the Republican Party is rallying around libertarian ideals.

Paul inherited the problem of libertarian purity from his father, Ron Paul, who served three stints as a congressman from Texas and sought the Republican nomination for president in 2008 and 2012.

The younger Paul campaigned for his father, but is now edging away warily. Invoking Barry M. Goldwater is hazardous for a Republican these days.