Suicidal Tariffs President Trump irrationally announced that he would impose 5 percent tariffs on goods from Mexico in less than two weeks and take them to 25 percent by October if Mexico City fails to stem the tide of illegal migration. Its irrationality is attested to by the reaction of the markets. Mexico is sending a delegation to Washington to discuss the matter, but it is a lose-lose proposition for several reasons:

Mexico will simply retaliate in kind, ensuring that it is equally painful on both sides of the border. Democrats can’t complain about his getting tough on China, but they oppose Mr. Trump on immigration and will have a heyday over the new tariffs. Mexico can doubly retaliate by not only issuing its own tariffs...