Biden and Trump are both old. So why are voters keying in on only one of them?

If he wins the presidency next year, he’ll be the oldest person ever elected to the White House.

Yes, that would be President Joe Biden. But it would also be former President Donald Trump.

Biden was the oldest presidential winner ever, when he won in 2020. The fact that he’d beat his own record is a historical footnote that has voters concerned.

Trump is no spring chicken either. In fact, he’s just three years younger than Biden. But he’s not facing nearly the same scrutiny for his age.

“Trump just comes off as a much younger person,” said Renee King, a two-time Trump voter in Mondamin, Iowa, who is undecided for 2024. (King declined to give her age.) “Just the way he speaks, the way he walks. Just everything he does.”

“He’s more into social media,” said Jane Story, 56, a Trump supporter in Ames, Iowa. “I mean, anybody has to learn with the times. And I just feel as though Trump has moved with the times and Biden has not.”

Dawn Brockett, 57, an independent from Hampton, New Hampshire, said Trump seems like he’s “blessed with that ability to — like a Mick Jagger, like he’ll be young forever.” Brockett said she plans to write in a candidate if the general election ends up being Biden against Trump.

NBC News interviewed dozens of voters in roughly half a dozen states about why Biden’s age is more of an issue than Trump’s. The responses showed that voters of all ages are concerned about whether Biden is up to another full term in one of the world’s most demanding jobs, although many also said that they’d like to see more younger candidates across the board.

“No doubt in my mind, I will vote for Biden. But we need age limits in politicians, and I would like to see much younger candidates,” said Tammy, a Democratic voter in Geauga County, Ohio, who declined to give her last name.

Mary Miller, 60, from Novelty, Ohio, voted Republican much of her life but supported Hillary Clinton in 2016 and Biden in 2020. She is happy with Biden’s performance but says she does worry about his age.

“When I listen to him speak publicly, I kind of hold my breath sometimes,” she said. “But you know, he’s the guy we’ve got, and … I don’t think it’s such a bad thing.”

When it came to Biden and Trump, some also thought the age gap was bigger than it really is.

Lisa Dumont, 49, a voter from Salem, New Hampshire, who voted for Trump twice but now backs former South Carolina Gov. Nikki Haley, said Biden’s age was a “huge problem” because Biden “can barely speak.”

She guessed the president was 86 (he’s 80) and Trump is 75 (he’s 77).

Story, from Iowa, shaved some years off both men, guessing “70-something” for Biden and “60-something” for Trump.

But for the most part, voters were pretty close in knowing — or guessing — their ages. And for them, it was just a number.

Trump, they said, has simply aged better.

“It’s genetic,” said Ilia Charlat, 53, from Bedford, New Hampshire, who plans to back Florida Gov. Ron DeSantis next year. “It comes from that, and lifestyle, but just you can see that … Biden is just an older person. … You can see [with] Trump how quick he is.”

“It’s not really age. It’s how you function at that age, rather than anything. And Trump functions a lot better than Biden,” said Isiah Chamberlain, 18, from Rindge, New Hampshire, who plans to vote Republican.

Trump, of course, has done everything he can to make Biden not seem up for the job. Since the 2020 election, he’s called him “Sleepy Joe” and questioned his intelligence.

“You look at him, he can’t walk to the helicopter. He walks — he can’t lift his feet out of the grass,” Trump told conservative pundit Tucker Carlson last month.

“He’s physically incapable and he’s mentally worse than physical,” Trump added in a Sept. 2 interview with Real America’s Voice. “And if he gets to the starting gate, it would be a miracle to me.”

Several voters also picked up on unproven or false talking points on the right, including that Biden may have dementia or even that his occasional stuttering is proof of his decline. (Biden has stuttered since he was a child and has spoken openly about working to overcome it.)

Virgil Thorstenson, 74, an ardent Trump supporter from Waukon, Iowa, had an even more dramatic theory of what’s going on with Biden: “His cognitive abilities have deteriorated greatly. … I don’t think Biden is in control. I think he’s a puppet being controlled by somebody else.”

Maxine Wheling, 62, a Republican voter from Gering, Nebraska, said she feels “bad” for the president.

“I feel like he’s being pressured and propped up, which I don’t feel is right,” she said. “I think he’s lived out his life. Enjoy his retirement time with his family.”

Tom Johnson, 59, a Trump supporter from Rapid City, South Dakota, said he felt like a big difference was that the former president’s wits have been tested.

“I look at what they did to President Trump,” Johnson said. “They tested him as far as they gave him this test on his IQ. I mean, he aced it. And, you know if Joe Biden could do that, fine. But we know that he can’t.”

In 2020, Trump liked to boast that doctors had given him a cognitive test and that he had “aced it,” using it as proof of his mental fitness. He said the doctors told him, “‘That’s amazing. How did you do that?’”

“I do it because I have, like, a good memory, because I’m cognitively there,” Trump said.

But it wasn’t an IQ test. It was a 10-minute test designed to detect mild cognitive impairment or early dementia.

Trump’s boast came at a time when he, too, was facing questions about his physical and mental abilities after being caught unsteadily walking down a ramp and appearing to struggle drinking a glass of water.

This cycle, it’s Biden who is battling more scrutiny. Over the summer, he tripped at the Air Force Academy’s graduation ceremony. Last year, he called on a congresswoman at a public event — even though she had died a month earlier. More recently, he wrongly said he was at ground zero the day after 9/11 when he was actually there a week later.

The 9/11 comments came right at the end of a whirlwind international trip — the type of travel that can be grueling and exhausting for people no matter their age, and something that Trump doesn't have to do as much as a presidential candidate.

Biden has also had to deal with some misinformation, including the false claim that he fell asleep during a memorial for the Maui wildfire victims. Conservatives — including Fox News host Sean Hannity — circulated a low-quality video on social media to push the claim, even though a clearer version of the moment showed that the president simply looked down for about 10 seconds.

Biden has responded by starting to crack jokes about his age, with knee-slappers like: “I know I’m 198 years old,” and, “I know I look like I’m only still 29. But I’ve been around a long time.”

Biden campaign spokesman Kevin Munoz pointed to Democrats’ wins in the midterms as proof that voters back the president and his party.

“Next year’s election will be a stark choice between President Biden and the extreme, unpopular MAGA agenda,” he said. “We’ll win in 2024 by putting our heads down and doing the work, not by fretting about polls.”

The Trump campaign did not respond to a request for comment.

Democrats, not surprisingly, are less concerned about Biden’s age than Republicans are — but that doesn’t mean it’s not a concern, or that they think it’s ideal.

“My real concern as a Democrat with Biden is that he won’t serve that whole second term,” said Thalia Floras, 75, a Democrat from Nashua, New Hampshire.

“We are in a country that is primarily controlled by older people, people who maybe have like five, 10, maybe one year left running,” said Gabriel Reynolds, 19, from East Greenwich, Rhode Island, who is a registered independent but leans Democratic. “I mean, we see people freezing up in meetings and stuff. It’s not good. We need to have people with a vested interest in the future of the world. We cannot be giving our world to the hands of those who are not long for it.”

As of now, it’s clear that age is on voters' minds, but it’s obviously not the only issue — and it doesn't mean it'll be a dominant issue a year from now. Trump is dealing with a number of legal problems, Republicans are figuring out how to neutralize abortion as an issue this cycle, and Biden is trying to pitch voters on his economic successes.

Roger Stephenson, 66, is a Stratham, New Hampshire, voter who voted for Biden in 2020 and would consider voting for him again. He was a Republican but switched away from the party to undeclared after Trump won in 2016.

Trump, he said, “has bigger problems than his age.”

This article was originally published on NBCNews.com