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CNN  — 

Joe Biden knows what it’s like to be the youngest guy in the room – he was sworn in as a senator at 30, the minimum age allowed by the Constitution.

We all now know what it’s like for Biden to be the oldest president in history – if he stands for reelection in 2024 and wins, he’ll be 86 at the end of a second term.

The people who wrote the Constitution adopted an age minimum for presidents – 35 – but they set no maximum, perhaps not realizing that hundreds of years later, people would be living much longer lives.

A defense against dynasties

One reason the framers agreed on a minimum age for presidents was to avoid American political dynasties, according to the National Constitution Center.

James Monroe, the future President who opposed ratification of the Constitution, said that 35 was a good minimum age because, “in the course of nature very few fathers leave a son who has arrived to that age.”

Times have changed. Biden is an outlier in the US for being a President who has lost two children, but he has a son who is 52 and a daughter who is 41.

25, 30, 35

There is an arbitrary feeling to the age minimums set by the Constitution. Starting with the minimum age of 25 set for members of the House, the framers added five years for senators and five more for president.

They set no age requirements or other specific qualifications for Supreme Court justices, including length of service, which is why the new conservative majority could be ensconced for generations.

The argument to step aside

While the Constitution allows for old presidents, political pundits are increasingly loud about questioning the wisdom of a Biden run for reelection.

The Atlantic writer Mark Leibovich wrote a plea in June titled, “Why Biden Shouldn’t Run in 2024,” for the President to bow out after one term. His argument was that the President is too old, although Leibovich was ashamed to admit it.

“It all feels impolite to point this out—disrespectful, ageist, and taboo, especially given the gross Republican smears about Biden being a doddering and demented old puppet,” Leibovich wrote. “No one wants to perpetuate this garbage.”

This weekend, The New York Times writer Peter Baker took a more analytical look at Biden’s age, reporting how the President spends most weekends at home in Delaware and calibrates his schedule to avoid especially long foreign trips and to tamp down on evening appearances.

Many presidents live very long lives

Biden doesn’t turn 80 until November and could well have decades of life ahead of him.

No US president has lived to 100, but recent presidents have all lived very long lives.

Jimmy Carter is the longest-living former President, a 97-year-old cancer survivor. Ronald Reagan, George H.W. Bush and Gerald Ford all lived into their 90s. But all these men enjoyed long retirements: 15 years for Reagan, 25 for Bush, nearly 30 for Ford, and 41 and counting for Carter.

We’ve seen this movie before

The oldest presidents often face questions about their fitness, typically in the form of whisper campaigns from their political rivals.

Donald Trump, who was in his 70s as President, frequently saw his temperament questioned. Reagan ultimately developed Alzheimer’s disease, but allegations that he showed symptoms in his final years in office have never been proven.

RELATED: Reagan didn’t have Alzheimer’s while in office

Running into their 80s

Biden’s old Senate colleagues routinely run for reelection in their 80s.

Sen. Charles Grassley of Iowa is running for reelection, and he turns 89 in September.

Sen. Dianne Feinstein of California, who is the subject of ageist questions about her fitness, recently turned 89, and her term lasts until the 2024 election.

Sen. Patrick Leahy of Vermont, on the other hand, decided last year when he was 81 not to run for reelection.

Other senators like Pat Toomey of Pennsylvania and Richard Burr of North Carolina seem downright young for planning to retire from the Senate while in their 60s.

Decades at the top

Nancy Pelosi, Steny Hoyer and James Clyburn, all in their 80s, have been top Democrats in the House since 2002.

If Democrats lose control of the House after November’s midterm elections, it would be an obvious moment for the party to begin looking to a new generation of leaders.

The facts vs. the smears

When The Atlantic column urging Biden not to seek reelection was published in June, CNN’s John Harwood tried to separate the valid questions about aging from the false and politically damaging idea that Biden is not cogent and capable.

“What’s true is the presidency is a hugely taxing job mentally and physically, and Joe Biden is old,” Harwood said on “Reliable Sources.” He added: “He doesn’t talk or walk as smoothly as he once did.”

What is not true is the trope pushed in conservative media that Biden is not currently mentally capable of doing the job. The President is engaged and acute, Harwood said.

Majorities have concerns

When I asked CNN’s polling editor Ariel Edwards-Levy for recent examples of public opinion on Biden’s age, she provided multiple examples of majorities of Americans thinking Biden’s advanced age is an issue:

  • In a November 2021 Fox poll, 53% of registered voters said that Biden’s age was interfering with his ability to serve effectively as President, and 40% said it was not.
  • In a February 2022 ABC News/Washington Post poll, 40% of US adults said they thought Biden “has the mental sharpness it takes to serve effectively as president,” while 54% said he did not.

Discomfort with Biden’s age extends to Democrats as they look to the next presidential election:

  • A New York Times/Siena College poll released on Monday finds that 64% of voters who intend to vote in the 2024 Democratic primary would prefer a nominee other than Biden. Among the group who would prefer a different nominee, 33% say that their reason for wanting someone different is mostly to do with Biden’s age, with another 3% citing his mental acuity.

Beating back age questions in 2020

Biden overcame many younger Democratic candidates to win the nomination in 2020, when the top priority for many voters was simply to defeat Trump. Voters will have other things on their minds in 2024, particularly if Trump is not a candidate or does not win the GOP nomination.

Edwards-Levy also argued that people’s attitude toward politicians’ ages can often be at least partially a reflection of how they feel about that candidate more generally.

In other words, Biden’s age is a problem so long as Biden is not popular.

Or, as Harwood said last month, “Joe Biden would look a little bit younger if he was at 50% (approval) than at 40%, but he’s not – and so he’s going to have to deal with these stories for some time.”