When Dwight D. Eisenhower weighed the pros and cons of running for a second term, one factor that concerned him was his age.

Arguing against a re-election campaign in his mind, he wrote in his diary in November 1954, was the need for “younger men in positions of the highest responsibility” at a time of “growing severity and complexity of problems that rest upon the President.”

He was 64 at the time.

Today the two leading candidates for his old job clock in at 77 and 81. Barring an unforeseen political earthquake, America seems destined to have a commander-in-chief well past typical retirement age for years to come no matter who wins in November. Donald J. Trump would be 82 at the end of the next term, and Joseph R. Biden Jr. would be 86.

Aging today, of course, is different than it was in the 1950s, and Eisenhower did decide to run again, serving out a second term and leading an administration that historians credit as formidable. But he experienced multiple serious health scares in office that tested his Cold War presidency, and it seems reasonable to assume that the country could be confronted with similar issues between now and January 2029, when the next term will expire.

The issue of age was thrust back onto the front burner with the special counsel report on Biden’s handling of classified information that described the President as a “well-meaning, elderly man with a poor memory” who had “diminished faculties in advancing age”. The report came the same week that Biden on two occasions referred to European leaders who are, in fact, dead as if they were still around and mistakenly called the President of Egypt the President of Mexico.

Trump quickly sought to capitalize on the special counsel report, issuing a statement through an aide calling Biden “too senile to be President”. But Trump has suffered his own bouts of public perplexity lately, confusing the leaders of Hungary and Turkey, warning that the country is on the verge of World War II, saying that he defeated Barack Obama instead of Hillary Clinton and referring to his Republican primary challenger, Nikki Haley, as if she were Nancy Pelosi, the former House speaker.

As a matter of politics, age has been a bigger liability for Biden than for Trump, according to polls, perhaps because of the President’s physical presentation, particularly the shuffle when he walks. Biden, who unlike Trump exercises regularly, has agreed that age is a legitimate issue to consider but grew incensed over the report by the special counsel, Robert K. Hur, and made a last-minute decision to summon cameras to the White House for a feisty night-time pushback.

“Biden clearly finds the conversation about his health and age exasperating,” said Jonathan Darman, author of Becoming FDR, about the health challenges of President Franklin D. Roosevelt. “This is understandable, particularly given Trump’s own advanced age, his apparent confusion and his frequent lapses of memory. But even if, as Biden and his aides insist, he is in excellent physical and mental health, he owes it to the country to have a frank and robust conversation about the topic.”

Neither candidate seems eager for that. Both have issued reports from doctors stating that they are in good shape, but neither has answered questions about their health at length. While the White House physician has been made available to reporters by previous Presidents, Biden has not seen fit to order his doctor to respond to detailed queries.

Even assuming both are fit for the presidency at this point, the harder question for voters to evaluate is whether they will be in five years. The dilemma for the country would be what to do if a President slips mentally or physically in a way that affects his ability to do the job but will not admit it or voluntarily step aside.

History suggests that Presidents do not willingly give up power no matter how impaired they may be, and the constitutional mechanism for removing them enshrined in the 25th Amendment is politically problematic. Among other things, it requires a vice-president and majority of the cabinet to declare that a President is “unable to discharge the powers and duties of his office”, which loyal appointees may be reluctant to do if the President does not agree. Even if they did, a defiant President could appeal to Congress, requiring a two-thirds vote by both houses to sustain his removal.

Some of Trump’s own cabinet members when he was President contemplated invoking the 25th Amendment to unseat him, but his vice- president, Mike Pence, refused to go along. The 25th Amendment provides an alternative: A panel created by Congress could declare a President unable to serve, but lawmakers have never formed such a body. When Representative Jamie Raskin tried to create a bipartisan panel of outside experts during Trump’s presidency, the initiative went nowhere.

After Eisenhower’s rumination on age in his diary, chronicled by biographers like Jeffrey Frank, the general-turned-President suffered a heart attack in 1955 and underwent surgery in 1956 for an obstruction caused by Crohn’s disease before nonetheless winning re-election. In 1957, he had a small stroke but completed his term in 1961. Like other Presidents, he convinced himself he was uniquely suited to the White House and ran again.

Eisenhower overruled aides who wanted to hide his condition from reporters, instructing his staff to “tell them everything.” The health issues “kept no one from voting him a second term,” noted Richard Norton Smith, a former director of the Dwight D. Eisenhower Center in Abilene, Kansas. “Indeed, that wound up educating people about the modern treatment of heart and other diseases once presumed debilitating — even if Ike found distasteful public depictions of his internal organs.”

Roosevelt was always struggling with the politics of health, forced to convince the country that he was up to the presidency when he first ran in 1932 despite having lost the use of his legs because of polio. Roosevelt clearly proved capable despite the disease, and Darman argues in his book that it made FDR a better, more empathetic leader.