A Republican presidential candidate and biotech entrepreneur, Vivek Ramaswamy, on Monday posted a video to X of himself playing tennis shirtless and sweaty. “Three hours of solid debate prep this morning,” he wrote.

The tweet got more than 45,000 likes and a mix of reactions. Some posted memes contrasting Mr. Ramaswamy to President Biden falling on the stairs of Air Force One. Others posted pictures of the Russian strongman, Vladimir Putin, riding shirtless on a horse. “Vivek, where is your shirt?” Megyn Kelly replied.

Mr. Ramaswamy’s shirtless video comes two months after a Democratic presidential candidate, Robert F. Kennedy Jr., posted his own “debate prep” shirtless exercise video. In it, Mr. Kennedy is doing pushups in only a pair of fitted blue jeans, his tanned and surprisingly muscular torso on full display.

“Getting in shape for my debates with President Biden!” Mr. Kennedy wrote, a clear troll at Mr. Biden, who is unlikely to ever debate him.

Mr. Kennedy’s tweet also went viral but fueled speculation that the 69-year-old critic of the pharmaceutical industry was himself taking steroids. Mr. Kennedy later disclosed that he is on testosterone replacement therapy.

The message both candidates are trying to convey is clear: I am strong and healthy, and not a member of the gerontocracy.

The leader of the gerontocracy, President Biden also made a pectoral cameo earlier this month on a beach in Delaware. His saggy chest perhaps looked good for 80, but that’s the point: he’s 80 years old.

If Mr. Biden wins re-election, he will be 86 years old at the end of his second term — past the life expectancy of the average American man. Mr. Biden is also dogged by speculation about possible cognitive decline. His performance at Maui this week didn’t help.

President Trump is 77 years old, overweight, and fond of fast food. The silent generation and baby boomers hold half the seats in Congress. Speaker Pelosi is 83 years old. Senator McConnell had a “senior moment” at a press conference earlier this month, pausing mid-sentence until being shuffled off stage. Senator Feinstein is 90 years old and facing calls for her resignation after long absences from the Senate for health-related issues and after she gave power of attorney to her daughter.

As the first millennial Republican presidential candidate, 38-year-old Mr. Ramaswamy is running on a message of “generational change.” Several other candidates are making the same pitch. Ambassador Nikki Haley has even called for mental competency tests for candidates over 75 years of age.

“There’s nothing new about running as the leader of a new generation. John Kennedy did it in 1960. Bill Clinton did it in 1992,” a Democratic strategist, Hank Sheinkopf, tells the Sun. “It used to be about guys — men — running around hunting. That was the shirtless politician of previous generations.”

So will the shirtless-exercise video be a new campaign trend? Probably not. President Trump, Governor Christie, and Ms. Haley are certainly unlikely to release them. Clothed displays of physical health and strength, though, may filter into campaign ads and social media posts.

Mr. Ramaswamy for his part is doubling down. On Tuesday, he posted yet another exercise video to X, this time of him and his wife — both wearing shirts — doing burpees in what looks like a home gym. “More debate prep this morning, with my favorite sparring partner,” Mr. Ramaswamy wrote.  

Mr. Ramaswamy has been hesitant to criticize Mr. Trump, promising to pardon the former president if elected and even calling his own campaign “America First 2.0.” Yet the physical fitness videos offer a clear contrast to Mr. Trump, whose health — particularly if he is weighed at his booking in Georgia Thursday — could become an issue.  

Although pecs are unlikely to make an appearance Wednesday evening, age could come into play — and not necessarily in Mr. Ramaswamy’s favor.

Rising in the polls and positioned centerstage alongside 44-year-old Governor DeSantis, Mr. Ramaswamy will be facing older and more politically experienced candidates in the field. Mr. Ramaswamy has never held political office, and the other candidates are no doubt prepared to attack his foreign policy positions and 9/11 comments.

It might serve older candidates like Vice President Pence or Governor Hutchinson to recall President Reagan’s famous 1984 debate line: “I will not make age an issue of this campaign. I am not going to exploit for political purposes my opponent’s youth and inexperience.”

“In times of stress, people are looking for more qualified and more thoughtful leaders. Someone who has some experience,” Mr. Sheinkopf says. “If this campaign gets down to who could do more push-ups in a wife beater — or without, for lack of better way to call the shirt or T-shirt — then the country is in more serious trouble than we thought.”