“It’s one of the great hesitations people have, and it’s not just chronological age, it’s the perceived age, the performance,” said Dave Carney, a longtime Republican consultant who hasn’t decided whom to support in 2024.

Both Biden and Trump battled questions of their physical and mental acuity while in office with each insisting that their performance underscored their capacity to handle the rigors of the job. The 2024 election, likewise, will provide a window through which to judge them.

But an actual full-on campaign won’t start for quite some time. Trump, who faces a crowded Republican primary field, has begun holding campaign events and the occasional rally. And Biden, who faces no real intra-party challenge, has begun raising money and will have one-off political events, but his aides have signaled he won’t begin barnstorming until next year.

When the campaign does actually begin in earnest, both sides pledge it will not be an exercise in tapioca, “Murder, She Wrote” reruns, and early bedtimes.

Despite an age gap of only three years, the chatter around age looms larger for Biden, who moves noticeably slower than a few years ago. Members of his inner circle know the toll the job takes on any president, and they have seen him grow more easily tired.

If elected, he would be 86 at the end of his second term, nearly a decade older than the U.S. male life expectancy. Poll after poll shows that voters — including Democrats who approve of the job he has done — are not sure they want him to run again, with most citing his age as their top concern.

But Biden’s allies and most Democrats believe he is very much still up for the job. Biden has received clean bills of health from his doctors, and his advisers believe the 2020 race made clear that voters have grown more comfortable with older people in positions of power, whether in politics or business. “His age is not a surprise,” one adviser said recently.

For Biden’s team, age can often be reframed as wisdom. They argue he has been a steady hand during difficult times. And they tout an enviable legislative scorecard — including wins on infrastructure, guns and climate change. They also believe that the threat posed by Trump to the nation’s democracy will turn out voters, even if some of them have reservations about Biden.

“I love what the president says himself. He has a line where he says, ‘Just watch me,’” said Rep. Lisa Blunt Rochester (D-Del.), one of the campaign co-chairs. “Just watching what has happened just in the first two years, and then knowing what his plan is, as we move forward, we know that he is more than capable.”

But aides acknowledge that Biden’s final campaign will be more rigorous than the one he ran in 2020. That year, candidates were sidelined for months by the pandemic, with Biden setting up shop in his Delaware home to host virtual events, allowing him to largely avoid unscripted moments and the gaffes for which he is famous. This time, Biden will need to hit the road, though some of the travel grind is offset by having Air Force One at his disposal.

Aides are mindful of the schedule’s toll on Biden. He has few early morning events, allowing him to sleep in and exercise before starting most days. Breaks are built into his schedule, and down days are often incorporated after travel.

“Whether it was in Kiev, barnstorming the country highlighting the manufacturing jobs he’s bringing back, averting international crises in the wee hours of the morning like he did in Bali, or putting Republicans on defense over Social Security in the State of the Union, the American people and the world see his qualified leadership,” Jen O’Malley Dillon, senior White House adviser, said in a statement. “And younger aides have to push themselves to keep up with that pace.”

White House aides also point out that other presidents took down days after foreign travel and that Biden has kept a busier travel schedule so far this year than Obama did in 2011, the equivalent year of his presidency.

Trump, meanwhile, has previously tried to make Biden’s age an issue, with his nickname of “Sleepy Joe” and unsubtle assertions that the incumbent has lost a step. He has circulated memes of the president losing his balance walking into Air Force One and has called Biden “cognitively impaired” in rally speeches.

But those charges didn’t work in 2020 and Trump himself faces questions about his own age and fitness for the job. More recently, Trump has tried to distinguish between age and mental acuity, saying in interviews that he has friends in their 80s and 90s, like 93-year-old Home Depot founder Bernie Marcus, who are “100 percent.”

Trump kept up a more robust campaign schedule than Biden did in 2020. While Biden has worked and traveled — he journeyed to Ireland this month and is set for summits in Japan and Australia next month — Trump has been based at his resort in Palm Beach and has made frequent trips to early voting states. On Thursday, he heads to New Hampshire.

“President Trump continues to dominate in poll after poll, both in the primary and general elections. There is no other candidate in history who has the energy and stamina President Trump has, and he will out-work and out-pace Joe Biden to Save America,” Trump spokesperson Steven Cheung said in a statement.

Aides to Trump argue that the former president stays busy politicking from his clubs where he films policy videos, works the phones, and hosts fundraising events. And while he isn’t known to have the healthiest diet, Trump does keep active. In the morning he often zips around in his golf cart and plays nine holes before heading to his Mar-a-Lago office, where he’ll meet with advisers, lawmakers and candidates seeking his support, and he’s often out late into the evening socializing with club members and playing DJ for guests on the private patio.

As the campaign heats up, aides to Trump say he will keep a busy travel schedule and continue to criss-cross the country via his private plane to events and unannounced stops where he can show off his retail politics skills. They believe the campaign schedule alone will be an effective contrast with Biden — a chance to portray Trump as sharper than Biden in speeches and interviews.

“We really don’t have to say much,” said an adviser to Trump. “The contrast in energy and stamina will be demonstrated — and is being demonstrated right now — and that’s a contrast that will play itself out on the campaign trail.” Both Trump and his team have pointed to Biden’s presidential announcement, which came in the form of a short video instead of an event, as an example.

“Trump is older, too, but he doesn’t act as old as President Biden, he comes across as more vigorous and having more energy and that helps him avoid the same kinds of conversations,” said Carney. “And everyone else is going to talk about how we need a new generation, or some cliche along these lines for the rest of the campaign.”

Both Biden and Trump do face pressure from within their party to cede the way for younger lawmakers to take over. The president had framed himself as a bridge to the Democratic Party’s next generation. And GOP presidential hopefuls like Vivek Ramaswamy, 37, and Nikki Haley, 51, have framed their candidacies as a needed refresh for the party.

Haley has even proposed mental competency tests for politicians over the age of 75. Trump then went even further, saying that anyone running for office should face not only a mental competency test but a physical test as well.

Biden’s entrance into the race all but ensures that conversations that may have otherwise been considered taboo or even downright ageist will now become a centerpiece of a presidential campaign. Indeed, we may already have passed that point. During an interview Monday with Newsmax, Trump even darkly predicted Biden would not make it to the general election.

“It was hard to believe four years ago, but he was in the basement … it seems to me somewhere along the line something will happen,” Trump said.

Jennifer Haberkorn contributed to this report.