Shortly after receiving a diagnosis of pneumonia on Friday, Hillary Clinton decided to limit the information to her family members and close aides, certain that the illness was not a crucial issue for voters and that it might be twisted and exploited by her opponents, several advisers and allies said on Monday.
To those she did inform, Mrs. Clinton was emphatic: She intended to “press on” with her campaign schedule, she said. Her confidants concluded that she did not want to be challenged over her preference to keep the pneumonia private and continue working.
Mrs. Clinton’s inner circle was mindful of both her guardedness and her expectation of loyalty once her mind is made up. And she was optimistic that she could recover over the weekend, when she had only two brief events on her schedule, said the advisers and allies, who insisted on anonymity to disclose private conversations.
But Mrs. Clinton’s penchant for privacy backfired. On Monday, her campaign scrambled to reassure voters about her health, a day after she grew visibly weak and was filmed being helped into a van: unsettling images that circulated widely and led her aides to disclose the pneumonia diagnosistwo days after the fact.
In a phone interview with CNN’s Anderson Cooper on Monday night, Mrs. Clinton said she had kept her diagnosis a secret because “I just didn’t think it was going to be that big a deal,” and tried to shift the discussion to her Republican opponent, Donald J. Trump, and his lack of transparency.
“It’s really past time for him to be held to the same standards,” she said.
Mrs. Clinton’s aides acknowledged that they should have been more forthcoming and said she would release more details about her physical fitness and medical history this week, a concession to the political pressure that she is under because she chose not to reveal her diagnosis sooner.
But the manner in which Mrs. Clinton’s illness became public has also revived concerns among supporters, and criticism among detractors, about her seemingly reflexive tendency to hunker down, often citing a “zone of privacy,” when she senses a political threat. Her desire for tight control over personal information deepened during the partisan wars of the 1990s, influenced her use of a private email server as secretary of state and now threatens to make her look, again, as though she has something to hide.
“Usually you would think that the truth sets you free, but in the experiences that Hillary Clinton has lived through, that’s not necessarily accurate,” said Jay Jacobs, a Democratic Party leader in New York and close ally of the Clintons.
Referring to 1990s investigations of the Clintons, he said: “Whether it’s Whitewater or Travelgate or other things, when the facts came out, it still didn’t solve the problem. They did nothing wrong, but there was still controversy. She is a very private person, and she would rather not put out information that she did not feel needed to be shared.”
The new onslaught of questions about her health and medical records has been deeply frustrating to Mrs. Clinton and her team, who have sought to highlight the disparity between her and Mr. Trump over issues of transparency. Mrs. Clinton has released her tax returns, while Mr. Trump has not. She has provided exhaustive details about her policy proposals, while he has not. And she released considerably more medical information last year — in a letter from her physician, Dr. Lisa R. Bardack — than Mr. Trump did in his doctor’s letter, which contained little more than over-the-top boasts about his “strength and stamina.”
Yet as much as they want the pressure to be on Mr. Trump, Mrs. Clinton and her advisers are now on the defensive.
“She has been totally transparent on the important issues, including public policy ideas, far more than Trump,” said former Representative Barney Frank of Massachusetts, a longtime ally of Mrs. Clinton’s. “But there’s also a combination of a natural desire for privacy and the fear that information will be politically misused.”
Mrs. Clinton has long relied on a tight-knit, intensely loyal group of aides who share her instincts for political warfare and her skepticism and even hostility toward calls for fuller disclosure. Some of these advisers, like Huma Abedin and Cheryl D. Mills, have worked with her since the 1990s, when Mrs. Clinton complained that a “vast right-wing conspiracy” was targeting her and her husband, President Bill Clinton.
Ms. Abedin and Ms. Mills were among those Mrs. Clinton told of her diagnosis on Friday. Neither replied to emails on Monday.
Her campaign manager, Robby Mook, said Mrs. Clinton had not wanted her illness to deter her. “She just wanted to plow through it,” he told MSNBC, “and I think that’s part of what’s going to make her a great president.”
But trustworthiness is a glaring problem for Mrs. Clinton. Roughly six in 10 voters said they did not trust her, about the same percentage who said they distrusted Mr. Trump, according to a Washington Post/ABC News poll released last week.Most voters have not been moved by questions about Mrs. Clinton’s health: 74 percent of registered voters said they were unconcerned about her being healthy enough to carry out the job of president, a Fox News poll last month found.
Mrs. Clinton had several opportunities before Sunday to disclose that she had pneumonia, including one at a news conference on Friday where she discussed her plans to defeat the Islamic State, called for a rethinking of the Obama administration’s approach to North Korea and ridiculed Mr. Trump’s praise for the Russian president, Vladimir V. Putin.
(At a fund-raiser that night, Mrs. Clinton, known for more calibrated phrasings, loosely suggested that half of Mr. Trump’s supporters fell into a “basket of deplorables” — bigots of one kind or another, essentially. She apologized the next day.)
On Sunday morning, when reporters learned that Mrs. Clinton had departed early from a ceremony in Lower Manhattan for the 15th anniversary of the Sept. 11 attacks, a campaign aide said only that she had been “overheated.”
The events quickly intensified pressure on both Mrs. Clinton, 68, and Mr. Trump, 70, to be more forthcoming about their health and medical histories. Mr. Trump has said he will release more medical information this week.It was not until more than five hours after the startling video surfaced online, showing an ailing Mrs. Clinton being helped into a van, that her campaign released a statement from Dr. Bardack saying Mrs. Clinton had been told she had pneumonia and put on antibiotics. The statement said she had become dehydrated and overheated at ground zero.
But they also reinforced a central vulnerability for Mrs. Clinton that has nothing to do with physical well-being.
“Antibiotics can take care of pneumonia. What’s the cure for an unhealthy penchant for privacy that repeatedly creates unnecessary problems?” David Axelrod, a former adviser to President Obama, wrote on Twitter.
Clinton aides have ample reason to be careful on the subject of her health: Political opponents on the right have spread a variety of conspiracy theories insinuating that she is physically unfit for the presidency, and Mr. Trump has fanned those theories, repeatedly questioning her “stamina.” After Mrs. Clinton had a coughing attack last week, Matt Drudge, editor of The Drudge Report, posted a spoof photo of her traveling press corps wearing surgical masks on her campaign plane.
But on Monday, her campaign acknowledged its error. “We could have done better yesterday, but it is a fact that public knows more about HRC than any nominee in history,” Jennifer Palmieri, a spokeswoman, wrote on Twitter in response to Mr. Axelrod.
Mrs. Clinton does not plan to return to the campaign trail until Thursday at the earliest, advisers said, and it is unclear how she and her doctor will respond to interview requests about her health.
Late Monday, she expressed gratitude to well-wishers. “Like anyone who’s ever been home sick from work, I’m just anxious to get back out there. See you on the trail soon,” she said on Twitter, signing her post “H” to indicate that she had written it herself.