To understand the concern, and in some cases the panic, of many Republican officials over Donald Trump, consider this fact: Young people generally donÂ’t like him. The potential of losing an election is one thing, but as polling numbers suggest, the Trump brand could weigh on the G.O.P. for a generation. â– In a recent USA Today/Rock the Vote poll, respondents under 35 said they would pick Hillary Clinton over Mr. Trump, 52-19. Those lopsided numbers would be hard to reverse if Mr. Trump were the nominee because he is such a known quantity. When the respondents were limited to...