Hillary Clinton was escorted from the September 11 commemorations at Ground Zero supported by a woman in a navy dress. And, as the woman held on to her arm, appearing to take her pulse, the Tennessee branch of the Republican Party tweeted that the woman could be Mrs Clinton’s “undercover nurse”.
The concept caught fire on social media – despite the fact that it would not be remarkable for presidential candidates to have medical professionals on standby, and that it would be strange for her medical professionals to be dressed in a nurse's outfit.
Others even repeated wild, widely-ridiculed claims that she was suffering from early Parkinson's disease.
Mrs Clinton's doctor, Lisa Bardack, confirmed in a statement on Sunday evening that she had diagnosed Mrs Clinton with pneumonia on Friday, and advised her to rest. Dr Bardack stated that Sunday's episode occurred due to the combination of that diagnosis, dehydration and overheating.
But critics of the 68-year-old used the latest health scare to paint a picture of a woman too elderly and infirm to be president.
In 2009 she fractured her elbow and needed surgery, and in 2012 she fell and suffered a blood clot on the brain. Conspiracy theorists have suggested that this has left her with permanent mental issues.
But Dr Bardack disagrees. In July 2015 she released an assessment of Mrs Clinton's health.
"Mrs Clinton is a healthy 67-year-old female whose current medical conditions include hypothyroidism and seasonal pollen allergies. Her past medical history is notable for a deep vein thrombosis in 1998 and in 2009, an elbow fracture in 2009 and a concussion in 2012," she wrote.
"She participates in a healthy lifestyle and has had a full medical evaluation, which reveals no evidence of additional medical issues or cardiovascular disease. Her cancer screening evaluations are all negative. She is in excellent physical condition and fit to serve as president of the United States."
Donald Trump's doctor, Harold Bornstein, then released a letter in December 2015 that lacked much medical detail, but noted that Mr Trump would be "the healthiest individual ever elected to the presidency".
Dr Sanjay Gupta, CNN's medical correspondent, found such language in the letter to be surprising and "almost comically" lacking objectivity.
Many doctors have called for both candidates to be subjected to assessment by an independent, third-party doctor.