In November, 1954, Dwight D. Eisenhower was mulling a matter that he mulled with some frequency: the effects of age on someone in a stressful, non-stop job like his. He’d been President for nearly two years and, in his diary, wrote down some of the reasons why seeking a second term might be a bad idea: “The greater likelihood that a man of 70 will break down under a load than a man of 50,” a need for “younger men in positions of the highest responsibility so as to symbolize the youth, vigor and virility of the Republican Party,” and, perhaps above all, the “growing severity and complexity of problems that rest upon the President for solution.” As far as he knew, he was in good shape, but intimations of mortality shadowed him, and he thought a lot about the next political generation. At a White House political dinner a few days before Christmas, he said, “We have got to begin right now, at the state level and at the precinct level, to see to it that the Party puts up the right kind of young man to run in ’56. All the programs in the world, and all the Eisenhower prestige, cannot elect some revolting old Republican hack against a youthful, able, and personable Democrat.”

Modern readers will note a certain gender bias in phrases like “a man of 70,” “the right kind of young man,” and “virility,” and should know that these somewhat depressed observations came soon after the midterms, in which Democrats took control of the Senate and House, by majorities that the party would keep for decades. Eisenhower’s worries became far more intense several months later, in late September, 1955, when he suffered a major heart attack.

This is a roundabout way of getting to the sensitive, impolite subject of when, if ever, a candidate might be too old for the Presidency. It is a question whose premise, in an era when the word “ageism” is embedded in the language, many are inclined to reject, in part because the motives for asking it tend to be suspect. The thuggish wing of the talk-radio community uses the age question to undermine Hillary Clinton, the Democratic front-runner, who will be sixty-eight in October. That makes her more than a year younger than Donald Trump, although age is the least of many concerns about him. Age should certainly count a lot less than the goofy ideas and inexperience demonstrated by too many Republicans. But the curious absence of a new political generation should concern Democrats, and a party whose other poll-leading 2016 candidates, declared and not, are Bernie Sanders, who is seventy-four, and Joe Biden, who will be seventy-three in November. (Barely registering in the polls are Jim Webb, who is sixty-nine, and Martin O’Malley, a relative teen at fifty-two.) Jeb Bush, Ben Carson, Carly Fiorina, and Mike Huckabee are in their early sixties, but, for better or worse, Republicans also have half a dozen contenders in their forties and fifties. The distinct problem for the Democrats isn’t the presence of elders; it’s the absence of young women and men with the potential to be credible national candidates.