For his many millions of supporters, in the United States and around the world, Sanders was not just a candidate; he was a rare opportunity. More than any other major presidential candidate in at least half a century, he represented the possibility of a drastic, and welcome, break from longstanding American orthodoxies and priorities in both domestic and foreign policy. Although many of his proposals—especially his signal demand for universal health care to replace America’s absurdly dysfunctional, wildly expensive, and criminally unequal profit-based system—are popular, older primary voters (those over the age of 50) roundly rejected him in favor of Biden, either because they were convinced by the media that Sanders was “unelectable” (this despite the fact that Sanders has bested Trump in every national poll since 2016, including in crucial swing states), or because they disliked Sanders himself....