Barack Obama famously aspired to be transformative like Ronald Reagan rather than incremental like Bill Clinton. What about Donald Trump? His friends and foes alike seem to share only the conviction that he changes everything. But it’s worth considering how lasting his legacy will prove to be. What will happen to the conservative populist movement that he masterfully discerned and harnessed—but did not create—after he is done?
Contrary to conventional wisdom, the real danger with Mr. Trump is that he may end up changing…