Ann Coulter has a gift for pushing just the right buttons to inflict maximum irritation. She has been a top-tier troll since Donald Trump was little more than a failed casino magnate. Which makes Ms. Coulter’s recent attacks on the former president — her onetime political idol — at once delectable and illuminating. Take her contrarian assessment of Mr. Trump’s chokehold on the Republican Party. [cut] Ms. Coulter, it seems, has found a shiny new leader with whom to antagonize her former hero.