This past June 27, the trim octogenarian took the spotlight. And against all medical odds, he moved through the evening like a teen in heat. Crisp as a hundred-dollar bill, he was nimble on his feet and never missed a beat or a word. He’s been doing this for decades, and he’s as strong and as vibrant as he’s ever been.

Alas, this wasn’t at the CNN studios in Atlanta; it was at Chicago’s Soldier Field. The man was Mick Jagger. And he will be the same age as Joe Biden at the end of this month. The thing is, there’s 81 and there’s 81. On some it can seem like the new 61—Harrison Ford, for instance. On others, as in the case of the president, it can seem like 101, as it did that night.

Atlanta Joe was looking highly senescent. That he was as white as a baby’s palm didn’t help. And like catching your parents having sex, you can’t unsee what you’ve seen. All the spin about his grasp of the issues and alertness isn’t going to work anymore. Visions of El Cid, the 11th-century Castilian ruler, who, though dead, was armored up and sent into battle, swirl around the mind.

There were suggestions that Biden should confine his workday to the hours of 10:00 a.m. to 4:00 p.m., with no evening duties past 8:00 p.m. You can’t really argue with that. Except of course if you’re president. And unless he’d hit the floor and done one-armed push-ups the way Jack Palance did at the 1992 Oscars, Biden’s Friday-night interview with George Stephanopoulos on ABC is not going to appreciably move the needle. Blue voters, especially male ones, are drifting orange.

We forget what old really looks like. Queen Victoria, who was on the British throne for so long they named an era after her, looked like an ossified mummy when she died. She was the same age Biden is now. Ronald Reagan was 77 at the end of his second term in office—and he was already falling victim to dementia.

Maybe we’ve been numbed by the way age is treated on television and in the movies. Betty White was 63 when she portrayed the more ancient of The Golden Girls. Lionel Barrymore was 60 when he played wily Martin Vanderhof, the grandfather in You Can’t Take It with You. And Wilford Brimley was 50 in the role of an old man in Cocoon. If the president is too old to play an elderly gent on TV, he’s too old to run the most powerful country on earth.

Biden is not helped by the serially pathetic stagecraft the poor fellow must work around. If you have an older candidate who takes tiny, delicate steps the way a man does if he’s trying on heels for the first time, don’t have him walk. Have him seated when the TV cameras start whirring. Take a page out of the F.D.R. playbook. And if he absolutely, positively must move around, make sure there are no obstacles in his way: last summer at the U.S. Air Force Academy graduation, in Colorado Springs, he tripped over a sandbag inches from his feet and fell hard.

Even agreeing to having the Atlanta debate at 9:00 p.m.—a time when most 81-year-olds are in bed—was an unforced error.

Joe Biden has been, to my mind, a transformative leader. And I believe that history will treat him kindly. But only if he realizes that the jig is up and doesn’t pull a Ruth Bader Ginsburg on us. You can survive health issues, and you can survive the brutal challenge of opponents and horrendous family tragedy. But you cannot beat the clock. Joe Biden is simply too old to run against his opponent. Trump might have spewed a lunatic flurry of half-thoughts and lies that evening in Atlanta, but he did it with such command that his fans and political supplicants saw his performance as winning and presidential.

Visions of El Cid, the 11th-century Castilian ruler, who, though dead, was armored up and sent into battle, swirl around the mind.

Trump, being Trump, gracefully shared his review of the night on his tiny social-media platform: “TRUMP WAS REALLY GREAT!” he declared. “In all fairness, and I say in complete and total modesty, many, on both sides of the political spectrum, have said it was the greatest single debate performance in the long and storied history of Presidential Debates.”

The word around Washington is that Jill Biden is running the show so far as her husband’s staying in the race is concerned. She and their son Hunter and the rest of the president’s enablers have been so intent on deceiving voters about his decline that it appears they wound up believing their own spin.

The trappings of First Lady are no doubt agreeable. But so are the trappings accorded a former First Lady. There won’t be a Vogue cover like this month’s epically badly timed one. (The single coverline was especially ill-advised: “We will decide our future.”) Letting her husband continue this way is, as many have said, a form of elder abuse. And it’s a cruel thing to do to the nation.

Party conventions, once cathouses of backroom bargaining and intrigue, are now so bland that the major TV networks don’t even carry them live. As Bill Maher has said, an open Democratic convention this August in Chicago would be reality TV at its very best.

Let the Republicans do their mash-up of The Golden Bachelor, MILF Manor, and “The Real Housewives of Mar-a-Lago” at their get-together in Milwaukee.

A Democratic convention that is a combination of Survivor, The Traitors, and Perfect Match would be something that would make Trump drool: a ratings bonanza. It would also allow the strong, youthful Democratic bench to show what it can do. Having Biden as a wise man at your side would be a bonus to any younger aspirant.

Almost as important, it would make the Republicans look old, angry, and orange. With the Democratic Party open to a new leader, their convention in Chicago would come alive as Soldier Field did on June 27 of this year, when the Stones were in full flower and Mick was bouncing around the stage like a 21-year-old.

Graydon Carter is the Co-Editor of Air Mail