A lot of very smart political people predict that Donald Trump will arrive at the Republican convention in Cleveland shy of the 1,237 delegates needed to clinch the nomination on the first ballot. Here’s why I don’t think that’s the way it will play out. To begin with, you’ve got to understand Trump’s mentality—and I believe I understand him better than most people outside his immediate family. I’ve known Trump for 35 years, met with him on numerous occasions, talked to him on the phone countless times, traveled with him, and written two lengthy magazine cover stories about him. One...