Washington (CNN) Joe Biden this week had a tense exchange with an audience member during an Iowa town hall who had asserted, among other things, that the former vice president is "too old" to helm the White House.

"You wanna check my shape on it, let's do push-ups together, man, let's run, let's do whatever you wanna do," Biden, 77, said.

While the 2020 Democratic presidential candidate has since downplayed the incident , his posturing was revealing. It's of a piece with a deeper stress in the Democratic race: The party is growing diversity-wise, but in important ways it's still marked by septuagenarian white men -- including Biden, former New York City Mayor Michael Bloomberg (77), and Vermont Sen. Bernie Sanders (78).

You could think of this trend as a fascinating foil for two of this year's most acclaimed movies: "Once Upon a Time in Hollywood" and "The Irishman."

The former, directed by Quentin Tarantino, charts a man's shaggy journey as he comes to terms with the fact that he's become a pop-cultural relic. And the latter, by Martin Scorsese, is a machismo-fueled gangster epic about how life wears you down.

The two films are thoughtful reckonings with aging, specifically with the atrophying of a certain, narrow performance of manhood and the attendant anxieties of that decline. Both also shine a light on how that same sort of rigorous reflection often doesn't happen in the stubborn, real-life political world -- but should.

Toward the beginning of "Once Upon a Time," Leonardo DiCaprio's character, an actor, clues viewers in on one of the movie's primary conflicts when he says to his stunt double, played by Brad Pitt: "It's official, old buddy. I'm a has been. ... If coming face to face with the failure that is your career ain't worth crying about, then I don't know what the f*** is."

His celebrity, which for years has hinged on the particular masculinity of mid-century Westerns , is losing its luster.

In a similar vein, Robert De Niro's mob figure, when looking back on his decades spent as part of the criminal underbelly, remarks: "Russell, he had a stroke. Fat Tony, he couldn't control his urine no more. And my arthritis, that started in the foxholes of Anzio, was eating away at my lower back now, and I couldn't feel much in my feet no more. I needed a cane."

It's a humble account of how time catches up with everyone -- big-boss men, too.

"('Once Upon a Time in Hollywood' and 'The Irishman' are) full of an awareness that a moment for a kind of movie -- and for a kind of long-celebrated male character -- is passing, perhaps deservedly," the journalist and film historian Mark Harris writes . "Both movies take as their subject the waning of an alpha-male primacy that has dominated film culture."

Different world

How different the world -- and people's appraisal of it -- is off the screen!

Consider Bloomberg. When the CBS News anchor Gayle King probed in an interview that aired on Friday about the narrative "Here we go, another old white gentleman" and how Bloomberg's candidacy is at odds with the Democrats' vision of change, the former New York City mayor dodged.

"Maybe. But lots of people can enter. If you wanted to enter and run for President of the United States, you could've done that. But don't complain to me that you're not in the race. It was up to you," Bloomberg said.

It was a guarded response, one that was telling of the times in how it seemed to breezily disregard a bit of recent news: the fact that California Sen. Kamala Harris, who was the race's only black female candidate, dropped out partly to avoid debt just shortly after Bloomberg had used his wealth to enter.

Or take, once again, Biden. Ahead of the Iowa caucuses in February, his campaign is testing out a slogan: "NO MALARKEY!" The point is to communicate Biden's cut-to-the-chase approach to politics. The term's mixed reception, however, is illustrative of the sentiment held by a number of people that a candidate with so much experience over so many years is out of touch today.

"While some voters welcomed the slogan as a throwback to a calmer era, others said it will only alienate younger voters," Politico's Natasha Korecki recently reported . "But many said, bottom line, they don't quite get it. ... Some Iowans offered up their own loose translation for malarkey, along the lines of: 'How old is this guy?' "

Endurance

You could make a similar argument regarding Sanders. The question of whether someone is past their prime has stalked him arguably more than his competitors, especially in the wake of his heart attack in October. The Vermont senator's health scare forced him to recalibrate his routine as he sought to prove that he's capable of leading.

But in another sign of today's not-like-the-movies political situation, Sanders appeared to gain momentum in the weeks after his campaign announced that he had been hospitalized. Likewise, his first comeback rally, held in New York City with Rep. Alexandria Ocasio-Cortez, attracted a reported 26,000 people -- larger than any of his rivals' events this year.

"Sanders' standing has only increased since he had that incident," the Iowa Democratic strategist Jeff Link told Politico in November . "It was a wake-up call for people who were totally committed to Bernie, like: 'We got to make this time count.' "

All of which is to say: These men -- ones like them -- don't seem to be going anywhere.

This isn't to beat up on the Democratic Party over its image problem. After all, the GOP is much more homogenous.

Rather, it's to highlight how, for a party for whom diversity isn't gloss, it still struggles mightily to reflect its base in a meaningful manner. And in some cases, there's a protectiveness over the status quo -- or at least a reluctance to challenge it.

Bringing the party's reality in line with its possibility will require that the Democrats ask themselves what "Once Upon a Time" and "The Irishman" quietly ask their audiences: What does the future look like? And how might we figure in it?