Bloomberg + Sanders + Biden + Trump + Warren = 374. What's wrong with this 2020 picture? Research shows older adults are slower to conceptualize problems and make changes when circumstances shift. How would that work in the Situation Room?

Peter Funt | Opinion contributor

Hallelujah. In Michael Bloomberg, Democrats have just what they need: another presidential candidate who was alive when Harry Truman occupied the White House. The former New York mayor and billionaire business tycoon is 77.

Until Donald Trump's victory in 2016, Americans had never elected a president who was 70 upon entering office. The age of the world's most powerful person is critically important, and most voters acknowledge it. Yet in the 2020 campaign, the issue is largely ignored. Why?

Back on Oct. 1, when 78-year-old Bernie Sanders suffered a heart attack, it set off a flurry of worry about aging politicians. But just a couple of weeks later, with the Vermont senator looking robust and his usual frisky self in a three-hour debate, opinion flipped. Sanders, many said, was living proof that age doesn't matter. In truth, neither Sanders' heart incident nor his declaration soon after that "I am back!" changed anything about the physical and mental odds facing older candidates.

We tend to evaluate politicians' fitness to serve based on the image they present in public. By that measure, Sanders looks vigorous now that he's back on the trail; Sen. Elizabeth Warren, 70, bounds around the stage with pep in her steps; Trump, 73, seems tireless delivering lengthy speeches at campaign rallies; and former Vice President Joe Biden, 76, appears lean and fit.

An age when odds turn against you

Then again, just a few days before being stricken in Las Vegas, Sanders seemed as healthy as ever. Trump's tan from a bottle might help project an image of physical well-being, but his actions in office have prompted many to question his mental health. Biden has fumbled badly in campaign appearances, placing his cognitive faculties in doubt. Only Warren, youngest of the leading septuagenarians, shows no outward signs of aging, but even she is at a point in life when the odds turn against you.

It’s not surprising that Trump supporters aren’t focusing on the president’s age. With impeachment proceedings dominating the news and the White House staff unraveling, age becomes the kind of thing the late George Carlin spoke of in his comedy weather forecast when he said: The radar is picking up Russian ICBMs, so I wouldn't sweat the thundershowers.

On the Democratic side, the goal of defeating Trump is so dominant that little else seems to matter. When Pew researchers asked Democratic voters about age, 97% said it would be better to have a presidential candidate younger than 70. Yet, the Real Clear Politics polling average shows about two-thirds of Democratic primary voters supporting candidates 70 or older — Biden, Sanders and Warren.

This disconnect might be due to voters’ understanding that people do age differently. They see vibrant public servants like House Speaker Nancy Pelosi, 79, and Supreme Court Justice Ruth Bader Ginsburg, 86, and dismiss concerns about the age of presidential contenders.

Uneasy feeling: Joe Biden isn't the boringly reassuring candidate Democrats were hoping for

Yet, the science of aging is clear-cut regarding factors that affect a president’s ability to serve. As people grow older, their ability to multitask diminishes, as does their recall of new or recently learned information. Here is one particularly pointed observation from a paper on aging by the noted author Dr. Diane Howieson: “Older adults tend to be slower in conceptualizing problems and less ready to change strategies when circumstances shift.” How would that work in the White House Situation Room?

Former President Jimmy Carter, a marvel of clear-headedness at 95, said recently that by the time he reached 80, “I don’t believe I could undertake the duties that I experienced when I was president. For one thing you had to be very flexible with your mind. You had to be able to go from one subject to another and concentrate on each one adequately and then put them all together in a comprehensive way.”

Avoiding reality of age concerns

Among the things that do improve with age is experience, which is often quantified as “wisdom.” Biden spoke of it in the October debate: “Look, one of the reasons I’m running is because of my age and my experience. With it comes wisdom.” When Sanders was asked about his health and age, he said: “We are going to be mounting a vigorous campaign all over this country.” Same question to Warren and a similar answer: “I will out-work, out-organize and outlast anyone.”

Three predictable responses, none of which addressed the reality about aging that concerns Carter. How older candidates look and sound today might be a good indicator of how well they would function tomorrow or next month. But the candidates are seeking a term that would end half a decade from now.

Maximum age: I'm the same age as Elizabeth Warren. We 70-somethings have no business being president.

Some Democrats would like Biden and Sanders to pledge to only serve one term. A related suggestion is they'd be wise to select a significantly younger running mate, who could step in if needed or move to the top of the ticket after four years. How awful. The process of replacing a president is traumatic for the nation and on the world stage, no matter what the circumstances. And betting that a vice president could move up and win the next election is no sure thing.

Carter believes there should be an age limit for presidents, which sounds like a good idea that comes from wisdom gained by experience. Of course, it’s too late for that sort of thing in the 2020 campaign. But there is time, when the primary-season voting begins in February, to thank the older candidates for their service and turn to someone younger.

Peter Funt is a writer and host of "Candid Camera."