Rand Paul has a little-discussed problem. Yes, he’s riding a wave. Yet another new poll brings happy tidings, putting him at the top of the GOP heap in both Iowa and New Hampshire (although still well behind “undecided”). He keeps doing these clever things that titillate the Beltway sages, like coupling with Democratic Sen. Cory Booker (ooh, he’s black!) on sentencing reform. All this, you know. He’s a shrewdie, we have to give him that. But here’s what you maybe don’t know. Paul is up for reelection in 2016. One assumes that he would want to hold on to his...