Thomas Jefferson could easily have won a third term as president. He was the most influential figure in the Democratic-Republican Party, which had displaced the Federalists to become the dominant political force in the United States. In the first decades of the 19th century, there was no limit on how many terms a president could serve and George Washington’s precedent of stepping down after eight years had not yet hardened into custom.

But Jefferson had no intention of remaining in office indefinitely. He looked forward to leaving the White House and was eager, in the words of historian Peter Onuf, to “satisfy his boundless curiosity for life.” His interests ranged from mastering Greek to managing his estate at Monticello to promoting scientific research. Above all he was absorbed with planning the new University of Virginia, from designing its campus to shaping its curriculum.

The ability to walk away from power is a great virtue in a democratic republic. It is also one that too many contemporary political leaders lack. President Biden’s disastrous performance in last week’s debate with Donald Trump reinforced what an overwhelming majority of Americans already believed — our octogenarian president lacks the cognitive agility a president needs, but he is determined to hang on to power nevertheless. A wide swath of voters also think Trump, 78, is too old for the White House.

Biden, 81, is hardly the only high political official who cannot admit that his time has passed. Washington today is more of a gerontocracy than ever. Senate minority leader Mitch McConnell is 82 and has had episodes of freezing up and staring blankly when answering questions. Senator Dianne Feinstein of California was 90 when she died last September, having steadfastly refused to resign despite her manifest inability to think clearly and function independently.

In May, Senator Bernie Sanders, who is 82, announced that he is running for yet another six-year term, his fourth. Nancy Pelosi is no longer the House speaker, but the 84-year-old is seeking a 20th term in Congress. Even more ancient is Senator Chuck Grassley, who has been on Capitol Hill since 1975 and will be 95 when his current Senate term ends.

In his legendary 1961 inaugural address, John F. Kennedy declared that the torch had been passed to a new generation. But America today is governed by ancient politicians who cannot bear to think of passing the torch to younger men and women.

There are some admirable exceptions.

Senator Mitt Romney of Utah announced last fall that he would not run for another term — not because he has lost interest in public affairs but because of his age. “At the end of another term, I’d be in my mid-80s,” Romney said. “Frankly, it’s time for a new generation of leaders.”

Senator Debbie Stabenow of Michigan likewise announced that she would leave Congress when her current term ends. Noting that she had been just 24 when she entered politics, the 74-year-old Democrat expressed the desire to make way for someone younger.

Ideology aside, the best public officials have always been those who know better than to overstay their welcome. John Glenn, the first American astronaut to orbit the earth, went into politics and served four terms as a Democratic senator from Ohio. When he announced that he wouldn’t be running for a fifth term, he said candidly that people his age — he was then 75 — were simply too old for the job.

“One immutable fact remains,” Glenn told an audience of college students. “There is still no cure for the common birthday.”

Alas, there is also no cure for the common politician’s ego. Many officials regard themselves as indispensable and are certain that no one can possibly do their job as well as they can. They cannot imagine relinquishing power voluntarily, addicted as they are to the perquisites of their office and the deference shown to them by mere mortals. Many have spent so many decades in office that they have no other identity; to give up their position is, at some subconscious level, to give up the one thing they care about.

It is a paradox of democratic politics that only those willing to walk away from power deserve to be entrusted with it in the first place. America’s gerontocracy has become a serious problem, but the solution is ultimately in the hands of the people. If we don’t want to be governed by elderly politicians, all we have to do is stop voting for them.