Transcript for Hillary Clinton's Health Scare Raises Transparency Questions

Hillary Clinton facing political backlash tonight over what's being called her lack of transparency. After revealing her previously undisclosed pneumonia diagnosis. This after weeks of the Clinton camp dismissing concerns about her health. As conspiracy theories here's ABC's David Wright on how this will impact. The election. It's not just the fact that she stumbled or worse that makes this news word considered the time and place. Ground zero on the fifteenth anniversary of 9/11. And Donald Trump both there to project strength and resolve. Worst terror attack ever on American soil an attack that hit close to home for both of them the world. So for Clinton to abruptly leave early without explanation. And then to appeared in nearly collapsed. It's bound to be a very big deal for the boxes of Florida and new questions tonight about Hillary Clinton's health moments ago because of remember parent medical up. So's I just didn't think it would. Going to be that big a deal like. Tonight clear and called in to Anderson Cooper to clear things out. There's a lot of folks are very worried about you how are you feeling. Oh thank you Anderson. I'm feeling so much better and obviously. I should've gotten some rap sooner I probably would have been better off that side. Just hold down my schedule on Friday. But the damage was done. After Clinton left ground zero a took her age ninety minutes to issue a statement that she felt overheated during the ceremony. And decided to head over to her daughter Chelsea's Manhattan apartment. Less than an hour after that she emerged still in sunglasses put all smiles ignoring reporters' questions as though nothing had happened. She even pause to hug a little girl who ran up to greeted. Then cheer for resent her advice. And zoomed home for the rest of the death. Five hours later another state this time from her doctor revealing that she was diagnosed Friday with pneumonia. Now knowing that she has pneumonia. Should she be blogging that child in the streets yet you know there are so many different types of pneumonia and some of them are contagious most of them are not. Even so today senator Chuck Schumer who stood next to her ground zero said Hilo has pneumonia. The campaign sent a number of staffers of the stricken choke the bug. Apparently going around. Clinton now following her doctor's orders hung back on schedule. Katrina tonight like anyone who's ever been home sick from work I'm just anxious to get back out there CU won the trail soon. Today Donald Trump appeared to take Clinton met her word. But I just hope she gets well and gets back on the trail. And will will be secured the debate. But for weeks now his campaign has been sowing doubts about her physical stamina. She doesn't have. This drank all of this stamina to make America great again believe me. Oh. Friends letting her persistent cough that flared up again a week ago. Everett to have a thing about drop my allergic. Today given her campaign's shifting stories some tough love from a fellow Democrat. Former Obama strategist David Axelrod treated. Antibiotics. Can take care of pneumonia what's the cure for an unhealthy penchant for privacy. The repeatedly creates unnecessary problems. I think it's clear that the campaign did not handle it well the fallout has been all those questions about her transparency about her honest about her trustworthiness. Good news for Clinton is that the health scare has taken the focus off for comments she made Friday night at a fund raiser you can put. Half of trump supporters and do what I called a basket of deplorable is. They're races sexes homophobic eggs that have followed and it. As Lama fall bag you name it. You cannot run for president. If you have sex content. In your heart for the American vote. And she does. But it's the health care issue now taking center stage and not in the policy sense. Clinton has a history of being less than forthcoming on this issue in 2012 when she was secretary of state. Clinton fainted at home while suffering from stomach bug. Banging her head and suffering what aides first described as a minor concussion. Months later at a Ben Ghazi hearing reporters noticed she was wearing present little prison glasses glasses designed to correct double vision. Only then there's her age revised their earlier disclosure admitting that the concussion was much more serious than they'd previously admitted. Speaking with Diane Sawyer in 2014. Clinton denied any lights throw them so no lingering effect no lingering effects and they can't help. The Republicans have had a field day. GOP strategist Karl Rove among the first to suggest that Clinton. Had suffered some sort of traumatic brain injury is this will be an issue in the 20s16 race and whether she likes and came. We saw. Diet others have taken it even further what honest could be the reason behind Hillary Clinton's bizarre behavior in recent weeks this viral video for instance suggests everything from seizures to STD's. Hillary on the verge of a mental breakdown. That the person has a seizure disorder business Heather David neurological problem. I think that's just nuts but it's not gonna stop people from doing it neither candidate has released full results from a physical both put out short notes from their doctors. And both now promised a more detailed disclosures sometime later this week. Personally as a voter. I'd like to know that a candidate is overall fit too impressed. That they don't have a condition that will impair their ability to carry out that job as a medical professional I know that there are conditions people could have. They will not have any bearing on that they Nino this year with the public I think that's people's right to keep that information private. There's a rich history of presidential candidates can ceiling significant medical problems most Americans had no idea FDR was confined to a wheelchair. Thanks to a complicit press corps who agreed to play down his disability from polio JFK suffered from Addison's disease a condition that can have a serious impact on the body's response to stressed. And of course Ronald Reagan's alzheimer's did not become public knowledge until well after he left office these are things it may have affected the elections. Should the public have known. I don't know. Vice president makes vice presidential vetting that much more important it does make a very important. Hillary Clinton's the most qualified person to run for president as tonight Tim Kaine prayed for Clinton's speedy recovery with questions about her health are all the more serious. Because of the larger narrative about her lack of transparency some. These questions about Hillary Clinton's health and stamina or on the dork reaches of the conspiracy theory Internet. And now is frightened finer in the campaign. Ironically Hillary Clinton has been talking for years about stumble when you're not. Right and back stumbling. Getting back up again goes to the heart of what she says would make for a good president. It's not whether you. You get knocked down that matters it's whether you get back pop. After this episode that challenge is now suddenly. Literate. I'm David Wright for Nightline in New York.

This transcript has been automatically generated and may not be 100% accurate.