Hillary Clinton's abrupt departure from a Sept. 11 ceremony in New York after falling ill Sunday and the subsequent disclosure that she is suffering from pneumonia are likely to intensify scrutiny on the Democratic nominee's health and potentially inject a new campaign issue into a race between two of the oldest candidates ever to seek the White House.
Clinton supporters had long dismissed concerns about her health as baseless, insisting that she only suffered from allergies. But Sunday's incident — along with a video appearing to show Clinton having difficulty standing on her own — will only amplify such questions just as the race enters its final weeks.
The incident also could increase pressure on Clinton, 68, and Republican nominee Donald Trump, 70, to release more information about their health. Clinton has disclosed less than some previous candidates. Donald Trump has released almost nothing.
"This is the kind of thing that voters have a right to understand before they cast a vote," said Katie Packer, a GOP strategist who says she does not support either Trump or Clinton.
"Both Trump and Hillary are elderly. They are obligated to release full medical records and full tax returns to the American people. And the media, party leaders and American people should settle for nothing less."
The pneumonia diagnosis comes as the campaign enters its most grueling phase, weeks before the first presidential debate and as voters start heading to the polls in states with early voting. Her doctor, who made the diagnosis Friday, has advised Clinton to curtail her schedule. But the Democratic candidate did not appear to skip any planned events over the weekend, including a fundraiser in New York headlined by Barbra Streisand.
After the incident, Clinton's campaign said late Sunday it was canceling a planned trip to California on Monday and Tuesday for fundraisers and a taping of "The Ellen DeGeneres Show."
Clinton's lung infection comes after a tough week for her campaign, with polls showing a tightening of the race against Trump. Then over the weekend, Clinton was forced to partially walk back comments she made referring to half of Trump's supporters as "deplorables."
The new scrutiny of her health will add to these problems.
"Forty-eight hours ago, this was something for the Flat Earth Society and the birth certificate deniers," Dan Schnur, director of USC's Jesse M. Unruh Institute of Politics, said of the speculation about Clinton's health. "Now it's a topic of legitimate, mainstream political discussion."
Although Clinton's opponents will surely make an issue of her having pneumonia, her campaign's relatively quick release of the diagnosis marked a significant step toward transparency for a candidate who has often shied away from disclosing information she considers private.
But some critics complained that Clinton did not reveal the potentially debilitating condition Friday when it was diagnosed. And after she fell ill Sunday morning, her campaign initially attributed it to "overheating" and waited nearly seven hours — as rumors and speculation about her health swirled — until disclosing the pneumonia.
For Clinton, perhaps the most damaging part of the day was the 19-second video of her struggling to leave the event in New York City. The video, quickly circulated online and replayed on cable news channels, shows her standing uneasily, her knees appearing to buckle and needing help to get into her van.
A spokesman said immediately afterward that Clinton left the ceremony at the site of the World Trade Center about 9:30 a.m. because she felt unwell. Reporters who were traveling with Clinton were not told about her condition or her whereabouts for 90 minutes after she left the ceremony.
"Secretary Clinton attended the Sept. 11th commemoration ceremony for just an hour and 30 minutes this morning to pay her respects and greet some of the families of the fallen," spokesman Nick Merrill said in the initial statement released by the campaign. "During the ceremony, she felt overheated so departed to go to her daughter's apartment, and is feeling much better."
The weather was in the low 80s and humid.
Clinton spent about two hours at Chelsea Clinton's apartment and emerged shortly before noon wearing sunglasses, greeting a young girl and waved at diners at a nearby restaurant.
"I'm feeling great. It's a beautiful day in New York," Clinton said before heading to her home in Chappaqua, N.Y.
Her personal physician examined her at her house Sunday afternoon and said Clinton was recovering.
"While at this morning's event, she became overheated and dehydrated. I have just examined her and she is now re-hydrated and recovering nicely," said Dr. Lisa R. Bardack in a statement. Bardack said Clinton was put on antibiotics Friday.
Clinton's health has long been the speculation of conspiracy theorists. In 2014, a People magazine cover of Clinton in her backyard leaning on a chair prompted speculation that she was leaning on a walker.
But innuendo about her health grew markedly during the presidential campaign as Trump and his surrogates, including former New York City Mayor Rudy Giuliani, routinely questioned her strength and stamina on the campaign trail.
Trump was uncharacteristically silent Sunday after news of Clinton's illness emerged.
Republicans have also pointed to coughing fits that Clinton has suffered while campaigning, and which she attributes to seasonal allergies. Her opponents have also raised questions about the effect of a concussion she sustained in 2012.
The drumbeat got to the point that Clinton poked fun at it on late-night television. During an August appearance on "Jimmy Kimmel Live," she pretended to exert great effort as she opened a jar of pickles and asked the host to check her pulse.
Clinton dismissed the attacks as "wacky" and noted that critics have claimed "I would be dead in six months," she said. "So with every breath I take I feel like I have a new lease on life."
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7:45 p.m..: This story was updated after the campaign announced the California trip was canceled.
4:40 p.m.: This story was updated with more reaction and analysis.