Republicans and former President Trump's supporters aren’t the only people that have questioned President Biden’s mental fitness for office, as anti-Trump pundits, mainstream news organizations and longtime Democrats have expressed concern in recent months, too. 

Billionaire Bill Ackman, a longtime Democratic Party donor, put a spotlight on a recent video of former President Obama appearing to guide Biden off the stage at a recent campaign donor event.

"Some people are old at 81 and others are sharp, vigorous, and impressive. Compare Warren Buffett at 93 and Biden at 81. Biden is an old 81 who can’t find his way off a stage or stay present and focused at a G7 conference. Is that who should be the leader of the free world for the next five years? A president should not have to be led off stage by hand or with an arm wrapped around him. That is the not the image of strength and leadership we need as a country," Ackman posted to X on Sunday.

"Look at what is going on in the world. The perception of weak leadership in the United States has led to global chaos. The reality of weak leadership is a long-term serious and continued threat to our country. The Democratic Party is destroying itself by advancing Biden for a second term," Ackman continued. "This is the Emperor’s New Clothes in real life. But it is not a children’s book or a joke. The world is at great risk, and a Biden second term is a grave threat to global security and prosperity."

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President Joe Biden

Many feel that President Biden’s age is a significant problem for the 81-year-old as he seeks re-election. (AP Photo/Andrew Harnik)

Ackman followed up by stating, "Biden is unfit to be president now and inarguably for another term."

On Monday's "Piers Morgan Uncensored," progressive journalist Cenk Uygur was critical of Democrats for not recognizing Biden's mental fitness issues, saying "we do all have eyes and ears."

"The guy is in terrible, terrible shape, and if he has dementia, they get more stubborn," he said. "What if he digs in, and he's like, 'I don't care,' and his mind is actually affected by the ailments that we’re seeing with our own eyes?"

Uygur added both Biden and Trump were "blithering morons."

The Biden White House has been on the offensive against reports of the president's mental decline, as polls show a wide swath of Americans are worried about the president's age. In February, a whopping 73 percent of Democrats said Biden was too old to serve. 

A report that month from the Department of Justice's special counsel called him an "elderly man with a poor memory" at the end of an investigation into his handling of classified documents dating back to his Senate tenure. The characterization ultimately helped save him from having charges brought against him by Special Counsel Robert Hur.

The Wall Street Journal, citing interviews with 45 people over the course of several months, reported earlier this month that congressional leaders and others who have met with Biden have noticed he "appears slower now" and is "someone who has both good moments and bad ones." 

The Journal's report prompted furious pushback from the White House and its allies, who have dismissed it as a GOP-led hit piece, much like Hur’s claims were largely rejected by Biden supporters on the left. However, Republicans aren’t the only ones making such claims. 

In February, former Obama adviser David Axelrod called the age and mental fitness issue a "problem for the president."

"There are things that reinforce a meme that’s out there that is hurting you. And the central meme that is hurting the president is this issue of age. It’s a big barrier," he told CNN. "People don’t give him credit for what he’s done. They blame him for everything that happens and a lot of it has to do with their feelings about his age. So it’s not wise to say to a reporter, ‘That’s your interpretation.’ It’s not. There are reams of polling material about this."

At 81, Biden is the oldest sitting president, and his critics say his age has caught up with him cognitively. He has been prone to gaffes and apparent memory lapses and will be 86 when his second term ends if he is re-elected in November.

Liberal comedian Jon Stewart, a frequent critic of Trump, the presumptive GOP nominee, recently said Biden "shouldn’t be president" because he is "so f---ing old," according to the New York Post. 

Another staunch Trump critic, billionaire Mark Cuban, has said Biden and Trump "both are going to have senior moments, mis-remember, forget things and have physical frailties."

President Biden

Earlier this year, a report from President Biden's own Department of Justice's special counsel called him an "elderly man with a poor memory." (Demetrius Freeman/The Washington Post via Getty Images)

"The View" co-host Sara Haines argued in February that it wasn't fair to tell voters to "close their eyes" on concerns about age and vitality. 

"Voters are concerned and by telling them they shouldn’t be or that they’re following a Republican narrative by listening to it, you’re literally saying, like, ‘Close your eyes to what you’re seeing,’ or you’re making them feel bad for raising something … I don’t think it’s fair to tell them to close their eyes to what they're seeing right now," Haines said. 

Co-host Alyssa Farah Griffin, who worked for Trump but is now a sharp critic, argued that Hur's report and Biden's subsequent fiery press conference in February showed that Democrats needed to put forward another nominee. She even proposed Vice President Harris could do the job in the aftermath of Hur spotlighting memory lapses by Biden.

Liberal comedian Bill Maher has at times called for Democrats to bench Biden ahead of the 2024 election, even selling "Ruth Bader Biden" merchandise featuring Biden dressed as the late Justice Ruth Bader Ginsburg.

Ginsburg chose not to step down during the Obama presidency, which later allowed Trump to replace her with Justice Amy Coney Barrett in 2020 following her death.

"He will be Ruth Bader Biden, the Ruth Bader Ginsburg of the presidency," Maher told Democratic strategist James Carville last year. "It's not a good look."

Earlier this year, Maher told Biden to lean into his age and stop trying to "deny the age thing."

"Lean in, lean in like you're eating soup," Maher said. "And just admit it! Say, ‘Yes, I’m bad with names and I walk like a toddler with a full diaper, but I believe in democracy."

Media mogul Charlamagne tha God has also said Biden "doesn't look full of vigor" regardless of what his supporters insist. 

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Even reliably liberal news outlets have put a spotlight on Biden’s age and mental acuity issues. 

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The New York Times recently published a story featuring a number of former Biden supporters explaining that perceived cognitive issues are the reason they plan to vote for Trump this time. 

The Atlantic's Mark Leibovich wants Biden to win again, given the alternative, but in a piece headlined "Ruth Bader Biden," he wrote that Biden’s candidacy remains an "existentially risky, perhaps disastrous, proposition." 

"No matter the obstacles Trump creates for himself, Biden remains a comprehensively weak incumbent, weighed down by the same liabilities that burdened him from the start, beginning with the largest, and completely unfixable, one: At 81, he is much too old to run for president," he wrote.

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The White House didn't immediately respond to a request for comment.

Fox News Digital’s David Rutz, Matthew Richter, Kristine Parks and Joseph A. Wulfsohn contributed to this report.