The speaker is exactly half the ex president’s age but his speech is the full Trump. “Joe Biden has turned the southern border into the world’s capital of drug trafficking,” says JD Vance, celebrity author of Hillbilly Elegy and Trump-endorsed Senate candidate for Ohio. To cheers from a capacity crowd in Youngstown, 1,500 miles from the Mexico frontier, he adds: “We do not have to allow the poison and the sex trafficking that’s flowing into our state thanks to the open border to continue to do so. We can shut that border, we can build the wall, and we can...