On Sunday, the health of Hillary Clinton moved from being an issue at the fringe of the US election campaign to a widespread focus of news and speculation.
The reason? She was filmed collapsing into the arms of her secret service personnel as she left a 9/11 memorial event in New York City.
Her doctor later released a statement to say the reason for the collapse was because Clinton has pneumonia, diagnosed last Friday.
"She was put on antibiotics, and advised to rest and modify her schedule," Dr. Lisa Bardack said. "At this morning's event, she became overheated and dehydrated.
"I have just examined her, and she is now re-hydrated and recovering nicely."
Despite Dr. Bardack's statement, questions about Clinton's viability to be the President of the United States are being raised as a result of this high-profile video.
However, this isn't the first time the Democratic candidate's health has been called into question.
Back in December 2012 - during her tenure as Secretary of State - Clinton was concussed after fainting in her home as a result of dehydration due to a stomach bug, according to her representation. At that time, she wore glasses to fix reported "double vision", suffered as a result of her fall.
Clinton's recovery was further complicated by the discovery of a blood clot a month later, and she was treated with blood thinners over several days in hospital.
All in all, the candidate took six months to fully recover from the concussion, according to her husband Bill Clinton.
Over the course of her current presidential campaign, Clinton has been seen to suffer from a number of coughing fits in interviews and events on the trail. One of the fits lasted two minutes during a Labor Day rally in Cleveland, Ohio last week. She passed it off by making a joke out of the situation, saying it was an allergic reaction to her opponent Donald Trump, her opposing candidate for the Republican Party.
Footage of one of the fits can be seen below.
Trump himself has - predictably - previously claimed that Clinton faces a health crisis, advancing claims she's suffered seizures by referencing selectively edited videos of public events.
From Clinton's camp, Dr. Bardack insisted her highest-profile client is fit for office. The candidate herself called Trump's claims about her health a "wacky strategy" during an appearance last month on the Jimmy Kimmel show.
"I don't know why they are saying this," she told the talk show host. "I think on the one hand, it is part of the wacky strategy, just say all these crazy things and maybe you can get some people to believe you."
Trump has previously insisted both he and Hillary Clinton need to release medical records. The question remains: for what reason has this not already been done?