Bill Clinton once explained the nation’s two political parties by saying that Democrats want to fall in love while Republicans want to fall in line. That adage has not withstood the Trump era. Today‚ it is Republicans who are besotted. Donald J. Trump’s decisive victory in Iowa revealed a new depth to the reservoir of devotion inside his party. For eight years‚ he has nurtured a relationship with his supporters with little precedent in politics. He validates them‚ he entertains them‚ he...