President Joe Biden, who turns 80 on Sunday, doesn't stick out in a US political class where young faces are so rare it has been called a gerontocracy -- though a changing of the guard may soon be afoot.

The outgoing speaker of the House of Representatives Nancy Pelosi, is 82. On the Senate side, gray hair prevails. Democratic Majority Leader Chuck Schumer will soon turn 72. Republican Minority Leader Mitch McConnell is 80.

But a light breeze of change is blowing in Washington, where Pelosi just announced she will not seek reelection as speaker to make room for "a new generation," and the second and third ranking House leaders, both in their 80s, are also stepping back from leadership -- though not resigning their seats.

Hakeem Jeffries, a frontrunner to replace Pelosi, is 52.

That is a full generation younger than some of his colleagues on Capitol Hill. At 89, Senator Chuck Grassley of Iowa just won election to his eighth term. At the start of his career in politics, in 1959, World War II hero Dwight Eisenhower was president.

Another senator, Richard Shelby, was born the year Adolf Hitler declared himself Fuhrer of Germany, in 1934. Now 88, he will retire at the end of the year.

And the case of Dianne Feinstein, an 89-year-old senator from California, has triggered debate on when it is time for aged politicians to call it quits. Feinstein is widely respected for her legislative career but she is said to have lost cognitive abilities and some wonder if she can still do her job.

If Biden runs and is re-elected as president in 2024, he could still be leading the country aged 86.

- Sea of gray -

The full makeup of the next Congress after the November 8 midterms is not yet known, as vote counting continues in some House races. But the average age of lawmakers in the outgoing legislature was one of the highest in US history: 58 in the House and 64 in the Senate.

The election has certainly ushered in some young new faces.

Maxwell Frost, a 25-year-old from Florida, will be the first House member representing Gen Z, whose interests he has pledged to defend.

"I think it's important that we have a government that looks like the people," he told AFP in October.

Answering to those who say his generation is impatient, he said: "I'd just say we know what we want."

He joins a small but energetic squad of young lawmakers on Capitol Hill.

One of the best known is 33-year-old Democrat Alexandria Ocasio-Cortez, darling of the party's most progressive wing and a lightning rod for criticism from conservatives.

But these young people are a tiny minority in a sea of older lawmakers, who also hold the most powerful positions in the legislature.

- Age limits -

Nearly three quarters of Americans think there should be an age limit for people serving in Congress, according to a CBS News poll published in September.

That sentiment is shared among Democrats and Republicans, and among younger and older people who took part in the poll -- a rare consensus in a deeply divided country.

"People do seem to be pretty positive toward having a younger representative," said Damon Roberts, a political scientist at the University of Colorado Boulder, but they "aren't really willing to translate that into votes."

There are built-in reasons why Americans have a tendency to elect people way past retirement age.

Consider these institutional barriers: you have to be at least 25 to serve in the House, 30 in the Senate and 35 to be president.

Americans also tend to see younger candidates as "less qualified to serve in office relative to a middle-aged or older candidate," as well as "more ideologically extreme," according to Roberts.

In 1984, Ronald Reagan wielded this argument with some wit as he sought reelection against the Democrat Walter Mondale, who was much younger.

During a presidential debate a journalist noted to Reagan that, at 73, he was then the oldest president in US history. Biden has since overtaken that title.

"I will not make age an issue of this campaign. I am not going to exploit, for political purposes, my opponent's youth and inexperience," Reagan said to loud laughter, even from Mondale.

© Agence France-Presse