Age isn’t just a number in 2024 — it’s also proving to be a major campaign weapon wielded by Republicans trying to recapture the White House.

The main target is President Biden, who at 80 years old is the oldest president in history running for reelection. But he’s not the only Democrat drawing attacks.

Sen. Dianne Feinstein (D-Calif.), 89, has been absent due to illnesses, prompting calls by younger Democrats to step down, while giving GOP candidate Nikki Haley, 51, an opportunity to buttress her campaign call for political mental competency tests.

The attacks illustrate how the GOP sees age as a way to defeat Biden in 2024, even as its party is led by a 76-year-old in former President Trump and an 81-year-old in Senate GOP Leader Mitch McConnell (Ky.).

Haley’s call for mandatory mental competency tests for politicians older than 75 was seen as a clear jab at Trump and Biden. The former South Carolina governor has specifically called on politicians to take the Montreal Cognitive Assessment, which is defined as “a brief, 30-question test that helps health care professionals detect cognitive impairments very early on.” 

On Monday, Haley called on Feinstein to resign in a Fox News op-ed as her team also released a video on the issue.

“What’s incredible is how the Washington establishment continues to cover for those who likely lack the mental acuity to do their job,” Haley wrote in the op-ed. 

Haley last week said that Biden would not make it to 86 years old — his age at the end of a second full term. It’s a way of telling voters that if they vote for Biden, they’re really casting a vote for Vice President Kamala Harris, 58.

“This uncertainty about Biden’s mental competence means Americans must consider the actual competency of the vice president,” Haley wrote in the op-ed, calling Harris “one of the most incompetent elected officials in the country.”

It’s not only a line of attack from Haley.

Sen. Tim Scott (R-S.C.), who is expected to run for the Republican presidential nomination, said in an interview with Fox News last week that a Harris presidency would be “a scary proposition.”

“The only thing worse than a Joe Biden presidency is a Kamala Harris presidency,” he added. 

Biden knows the attacks are coming and has sought to make light of them, cracking jokes at the weekend White House Correspondents’ Association dinner.

“You call me old? I call it being seasoned. You say I’m ancient? I say I’m wise. You say I’m over the hill? Don Lemon would say that’s a man in his prime,” Biden quipped on Saturday, referring to the former CNN host who faced controversy for saying Haley wasn’t in her prime.

Biden also signaled he sees a double standard in his treatment.  

“I get that age is a completely reasonable issue. It’s on everybody’s mind. And everyone, by ‘everyone’ I mean the New York Times. Headline: “Biden’s advanced age is a big issue. Trump’s, however, is not,’” Biden said.

Republicans constantly bash the president for showing his age, signaling they think it’s something on the mind of voters.

GOP strategist Doug Heye said it’s not an issue that is going away, and that while Trump is only four years younger than Biden, the fact Biden appears older is a problem.

“Trump is behind Biden so there’s that fact and, yes, every individual is different,” he said. “But also, whatever argument people make against Trump, and I certainly make a lot of them, his lack of stamina is not one of them.”

Trump is the GOP frontrunner, but other GOP candidates or would-be candidates are decidedly younger than Biden and Trump. 

Haley is 51, and Florida Gov. Ron DeSantis (R) is 44. Scott is 57, while former Vice President Mike Pence is 63. Businessman Vivek Ramaswamy is the youngest in the field at 37. 

Ramaswamy is the first millennial Republican to run for president, something he and his campaign have highlighted since he announced his bid earlier this year. However, his campaign says Ramaswamy is not campaigning on his age. 

“It’s less of a factor of age, it’s more of a factor of vision and acuity, and right now, clearly Joe Biden does not have the mental capacity to be commander in chief currently or for another four years,” said Tricia McLaughlin, a spokesperson for Ramaswamy.

Democrats have coalesced around Biden, who does not have a formidable primary challenger. Younger Democrats who took him on in 2020 have decided against doing so in this cycle.

At the same time, the age of some leaders and their perceived unwillingness to move on has been a theme in Democratic political circles in recent years — most notably in the House, where former Speaker Nancy Pelosi (D-Calif.) last fall decided to step down from leadership.

Feinstein is now under pressure to resign amid a series of health ailments.

McConnell has stayed in his position as the GOP leader in the Senate, though he was recently absent after being injured in a fall.

Republicans using age as a weapon against Democrats in 2024 could be a risky strategy, given their own octogenarian members and the possibility it could annoy some older voters.

But one GOP strategist brushed off such concerns, saying it would come down to who voters saw as competent.

“I’m from a state that elected Strom Thurmond and Fritz Hollings,” said Stroman, referring to the late South Carolina Republican and Democrat who were the longest-serving Senate duo in history.

“I’m happy electing a competent person in their 90s if they’re competent,” Stroman continued. “I don’t think it is always about age, and I think that was what Nikki Haley was arguing.”