The morning after the vice-presidential debate, Cathy Frasca woke at 5 a.m. and hand-wrote a four-page letter to Donald Trump that said: “It is obvious that you could easily lose this election.” The 89-year-old grandmother urged Trump to release his taxes, ignore the controversies that Hillary Clinton tries to start, stop tweeting at 3 a.m. and remember that “Bill Clinton is not running for election, so please avoid using precious time to discuss his sex life.” Instead, Frasca wrote, Trump should tell voters about how he will improve the country. “You know what to do but time is running out,”...