Did Biden even sign his own resignation letter? Bizarre new theory sweeps internet - complete with photographic 'evidence'

A wild conspiracy theory has started swirling on social media over claims that President Biden did not sign his resignation letter. 

The 81-year-old released announced he was standing down from his presidential race by sharing a letter to his social media on Sunday afternoon. 

Speculation has since started to grow, with conspiracy theorists poring over its authenticity, with some believing he never actually signed the letter himself.

His signature on the letter shared on Sunday show his name being underlined, which according to some commentators he has never done before.

Billionaire Bill Ackman has been one of those sharing the theory online, frequently reposting different takes on his signature to his X profile. 

The 81-year-old released announced he was standing down from his presidential race by sharing a letter to his social media on Sunday afternoon

His signature on the letter shared on Sunday show his name being underlined, which according to some commentators he has never down before in the past

Ackman, 58, shared one post that said: 'Lmao there's no way Biden didn't even sign the letter', alongside an image of different versions of his signature.

While another person posted: 'Yikes. Look at the B, totally different between the latest version and the previous ones. 

'The Jr. is also left off the most recent 'signature'. Wikipedia has an odd practice of including signatures, their copy also does not match the letter.

'So now the question is not just who wrote the letter, but who signed it? This really does look like a coup.'

Another commentator added: 'Now this is a conspiracy theory I can get behind. Biden is dead or some s***.' 

While others have said that without any physical proof of him signing the letter, either a video or picture, they will never believe he signed it. 

One person posted: 'No presidential seal, bad signature, and no video. I am calling bulls*** until I see video of Biden.'

The president has been isolating with Covid-19 at his holiday home in Rehoboth Beach, Delaware, when his team composed the letter. 

The president has been isolating with Covid-19 at his holiday home in Rehoboth Beach, Delaware, when his team composed the letter

Speculation has since started to grow, with conspiracy theorists speculating over its authenticity, with some believing he never actually signed the letter himself

Donors had pulled millions of dollars in funds, the list of Democrats telling him to drop out was growing by the day, and polls suggested that his chances of beating Donald Trump were dwindling after his disastrous debate performance.

Jill Biden was there when her husband eventually made the historic call, giving into mounting pressure. 

A spokeswoman for the First Lady said it was the president's judgment alone, and confirmed he made it late.

After his announcement, Kamala Harris announced she was running for the Democratic presidential nomination

Speaking with CBS, his younger brother Frank Biden said that the president's health was part of his decision to stand down.  

He told the outlet: 'I'm incredibly proud of my brother. Selfishly, I will have him back to enjoy whatever time we have left.'

That choice of phrase sparked speculation from Ackman and others that Biden has a secret illness he has not disclosed. 

A top Parkinson's disease specialist visited the White House multiple times this year, although officials have insisted Biden is in good health. 

'He is a genuine hero, country over self, it sounds corny in our cynical political environment but he nor I are cynical,' Frank's statement continued. 

'The goal remains the same, defeat Trump and continue the work that Joe has done. My hope is that our party rally's around this heroic act.'

When asked by the outlet if his brother's overall health played a role in him standing down for reelection, he said: 'In my humble opinion, absolutely'. 

On Saturday evening, Biden summoned to his side two men who have been there since his political start, advisers Steve Ricchetti and Mike Donilon. 

It was Ricchetti and Donilon who brought with them devastating new data which would help to make up Biden's mind.

They revealed the latest internal campaign polling, taken since the debate, which showed he could no longer beat Trump. 

Biden's decision was made soon after, and he asked Ricchetti and Donilon to start drafting a letter, and to begin the process of how to make a public announcement, DailyMail.com confirmed. The president also began telling his family.

After his announcement, Kamala Harris announced she was running for the Democratic presidential nomination. 

A number of prominent Democrats have since came out in support of Harris including California Governor Gavin Newsom.