Hillary Clinton used a body double to convince the nation she was healthy after she stumbled and left a 9/11 tribute early, conspiracy theorists have alleged.
Video footage showed Ms Clinton struggling to stay on her feet during the ceremony, and she had to be helped into a vehicle by Secret Service staff as she left the event early.
Her stumble was taken as "proof" by some of her opponents that she is seriously unwell and is unfit to be president.
However, Ms Clinton later made an appearance outside her daughter's flat in New York City, prompting supporters of Donald Trump to allege she was using a body double.
She was seen leaving her daughter's flat and waving to the crowd, before posing for a photograph with a young girl.
When a reporter asked her if she felt better, she replied: "Yes, thank you. I'm feeling great. It's a beautiful day in New York."
Ms Clinton's doctor said she was being treated for pneumonia and was "recovering nicely".
But conspiracy theorists claim Ms Clinton's health is far worse than reported and she has resorted to using a body double.
They pointed to perceived differences between photos of the presidential hopeful at both events.
Others suggested the photos actually showed Teresa Barnwell, a well-known impersonator of Ms Clinton.
However, Ms Barnwell later tweeted to say she was not in New York City and was "just messin' with your crazy conspiracy minded little heads," after she posted a photo of herself outside Chelsea Clinton's building.
Mr Trump has now promised to release a detailed report on his state of health.
