As the public media focuses on the upcoming November elections for House and Senate, a brewing battle within the Republican caucus in the Senate has been largely overlooked. Many ways exist to describe the two sides of this internal civil war—“true” conservatives vs. “RINO” Republicans; extremists vs. pragmatists; new generation vs. dinosaurs. But, as is usual in politics, the battle may be embodied in two senators—Jim DeMint of South Carolina and Mitch McConnell of Kentucky. DeMint has successfully endorsed candidates, Tea Party and otherwise, opposed by “establishment” Republicans. In Kentucky, DeMint’s choice, Rand Paul, defeated the candidate endorsed by McConnell...