How Much Is Donald Trump Hurting the G.O.P.? Here’s a Way to See

There is no reason to speculate about whether nominating Donald J. Trumphas cost the Republican Party support in this presidential election. There isplenty of data to demonstrate that it has.

Dylan Matthews of Vox showed one way of measuring the toll of choosing Mr. Trump over a candidate who more resembles past nominees. He considered the predicted election outcome for 2016 based on fundamental conditions that have long been known to affect presidential outcomes.