It wasn’t so long ago that Ronald Reagan was considered over the hill, too old to govern. Now a sitting President has turned eighty in office, and a Presidential contest between Joe Biden and Donald Trump would put two near-eighty-year-olds against each other. (Trump—while denying President Biden’s fitness—commented, “Life begins at eighty.”) Yet the question of age has not disappeared; even some of Biden’s ardent supporters have expressed concerns about him starting a second term. David Remnick talks with the gerontologist Jack Rowe, a professor at Columbia University who also founded Harvard Medical School’s Division on Aging, about how to evaluate a candidate’s competency for office; and with Jill Lepore and Jane Mayer, keen observers of the Presidency. Rowe argues that ageism underlies the public discourse; an occasional slip or unsteadiness, he thinks, is not consequential to the job. “If I give you a seventy-eight-year-old man with a history of heart disease, you don’t know if he’s in a nursing home or on the Supreme Court of the United States,” he tells Remnick. But Lepore and Mayer argue public opinion, and not only medical prognosis, should be considered seriously as we look at aging politicians. If Biden and Trump face off, Lepore says, “Age won’t be an issue between them. But age will be an issue for American voters. . . . I think of the young people that I teach everyday. They will be furious.” Mayer sees something anti-democratic in play as well. “Incumbency is such an advantage at this point,” she notes, that “it leads to gerontocracy,” because “it’s really hard to unseat someone.”