If the general environment fits Cruz nicely, the dynamic of the campaign is favorable to him, too. Ted Cruz isn’t topping the polls or dominating the conversation, but he’s one of the winners of the past few months. His odds of winning the nomination have increased more than anyone else’s besides Donald Trump, and if you believe (reasonably enough) that Trump isn’t built to last, more than anyone else’s, period. Let’s review. There was always the danger of Cruz, who made his national reputation on the strength of a misbegotten government shutdown, seeming like too much of a bomb-thrower. That...