The specious posts claiming to show Biden lost or freezing up underscore how increasingly bitter and personal the campaign has become online in the wake of former president Donald Trump's criminal conviction and as attack ads ramp up ahead of the first debates.
They also come amid some voters' worries over Biden's physical and mental condition, with Trump making age a top rallying point despite being, at 78, just three years younger.
The White House has branded the videos -- many of which originated with an X account run by the Republican National Committee, or RNC -- as "cheap fakes," a term misinformation experts coined to describe content altered using basic and affordable technology.
One short clip the "RNC Research" account shared this month shows the president hunching over during a ceremony in France to commemorate the anniversary of the D-Day landings.
Conservative influencers jumped on the 13-second footage, falsely accusing Biden of trying to sit when there was no chair behind him. Others insisted he had lost control of his bowels.
Rolling the tape further, however, makes it clear there was a seat beneath the president.
Jake Schneider, who runs the "RNC Research" account as the committee's rapid response director, told AFP the page has merely been posting clips that "come straight from pool feeds."
The account shared the D-Day clip with a caption that said "awkward." Conservative influencers then tacked on claims about an invisible chair and bathroom mishap.
But AFP fact-checkers found the RNC's video was cut to omit the ensuing footage, which revealed that Biden started to sit as the music stopped, paused to wait for Defense Secretary Lloyd Austin's introduction and then fully sat as Austin rose to speak.
'A playbook'
Zeve Sanderson, executive director of New York University's Center for Social Media and Politics, said selectively edited videos are effective because they are recontextualized or trimmed in less obviously misleading ways than wholly fabricated or AI-generated content.
Viewers may be inclined to take truncated, misrepresented or out-of-context footage at face value in part because there are also "some real clips of Biden being old," Sanderson said.
"They align with a sort of general sentiment that already exists in the public. If people thought that Joe Biden was young and sprightly, it's unlikely that these cheapfakes would be spreading as much," he told AFP. "This is a playbook that campaigns know is extremely effective."
In another video spread widely online, Biden appeared to stray from other world leaders and flash an errant thumbs-up gesture during a skydiving demonstration at the G7 summit in Italy.
After the GOP account highlighted the footage on X, the New York Post tagged Biden on its front page as the "Meander in Chief."
But the New York Post's cover photos -- and a video the newspaper shared online -- altered the clip's frame to crop out the parachutists Biden was congratulating.
The White House pushed back against the manipulation, and did so again after the newspaper and RNC account claimed yet another video showed the president "freeze" on a stage.
"It's telling that rightwing critics, including Rupert Murdoch's sad little super PAC, the New York Post, resort to misinformation and cheap fakes," Andrew Bates, White House senior deputy press secretary, said in a statement to AFP.
He said Biden's record "is so threatening to them that they feel a need to make things up."
White House Press Secretary Karine Jean-Pierre called Republicans "desperate" Monday.
Trump referenced the clips while accusing Biden of "humiliating our country on the world stage" during a Wisconsin rally Tuesday, repeating the online claims that Biden "froze" at recent events and "wandered" away from fellow leaders at the G7 conference.
Trump campaign communications director Steven Cheung told AFP the Biden team's comments are a "ridiculous" response to "cold, hard reality."
Polls show that a big majority of Americans think Biden -- already the oldest man to hold the office -- is too old, while a small majority think the same of Trump.
Against that backdrop, Sanderson said, "we're going to continue to see content that is about Biden's age, because that continues to be a concern amongst voters."