HOMEGROWN: Timothy McVeigh and the Rise of Right-Wing Extremism, by Jeffrey Toobin It was the dog whistle heard ’round the world. When Donald J. Trump decided to kick off his latest presidential campaign on March 25 with a rally at Waco, Texas, he was issuing a call to the far-right fringe that was earsplitting, even by his own standards. It wasn’t simply the location but also the timing: a month shy of the 30th anniversary of April 19, 1993 — a date that marked the fiery, deadly end of the 51-day standoff between the F.B.I. and David Koresh at his...