In a decade and a half of punditry, I’ve had to eat my share of crow for incorrectly predicting voter behavior. I was notably wrong about Brexit and wrong about the 2016 U.S. presidential election, calling them for Remain and Hillary, respectively. The opinion writer’s weakness for wishcasting is partly to blame. But voter preferences can also change quite rapidly. What polls suggest today can be completely upended tomorrow, let alone in several weeks or months. Having said all that—deep breath—I think Donald Trump is poised to sweep next year’s GOP primary. Or as The New York Times put it...