MIAMI BEACH, Fla.—Mitch Landrieu thinks Donald Trump “is wrong most of the time, because he takes a myopic, narrow view.”As he tells it, that’s not Landrieu the Democratic mayor of New Orleans talking, or Landrieu the heir to one of the most famous names in Southern Democratic politics, or Landrieu who gets chattered about as a dark horse Cajun entry into the 2020 presidential field.