— Joe Biden had been to Dachau, the infamous concentration camp in Germany, several times before, but he sensed changes when he visited as vice president with a teenaged granddaughter. "It seemed as though things had been rearranged to make visitors less uncomfortable,'' he recalled in a memoir published two years after the 2015 visit. ''They had softened the cruel edges over the years." Unwilling to settle for what he believed was a more sanitised experience, Biden asked the guides to bring them to the gas chamber, where they "slammed the door behind us with a frightening clank." For Biden,...