During last night's Republican presidential debate, the Wall Street Journal's Gerard Baker made a critical mistake: He tried to pin Donald Trump down on policy specifics. In this case, it was about trade policy, a subject about which Trump evidently knows very little. Baker asked the billionaire "which particular parts" of the pending Trans-Pacific Partnership free trade deal he objected to. If he were familiar with the deal, Trump could have raised any of several issues. Instead, he continued with the same word salad about China that he has been issuing forth since long before the TPP had been negotiated...