There is a pattern for how Mr. Trump reacts when cornered, and he was true to it last week. First, he made the usual vague, grandiose promises about how effective he will be once in office ("I will be so good at the military, your head will spin. ... I'm a delegator. ... I find absolutely great people and I'll find them in our armed services.") Then he attempted to kill the messenger, bashing Mr. Hewitt on Twitter as a "very low ratings talk show host" and a "3rd-rate gotcha guy."