But here, Boehner runs into a vicious circle: The more Democratic votes he needs, the more he will have to move the legislation to the left. And the more he does that, the fewer Republican votes he will attract. Eventually, he might be left with the Senate version of immigration reform, which makes a mockery of border security by throwing resources at the problem but requiring no solution before legalization begins. Boehner’s reassurance that he will not bring a bill to the floor without a majority of his own caucus behind it offers no consolation. A majority of the House...