The consolation prize in the great Senate GOP sellout on the Iran deal was supposed to be the opportunity it created to embarrass Obama. The fear was that if Republicans insisted on two-thirds approval of the deal for ratification, as the Constitution’s Treaty Clause requires, King Barack would simply reassure the public that this wasn’t technically a treaty and proceed to implement the agreement under his own executive authority. Heads he wins, tails you lose. That’s life in post-republic America. (And if you like that model, wait until President Trump is sworn in.) So Bob Corker and McConnell decided...