NEW YORK • Shortly after receiving a diagnosis of pneumonia last Friday, Mrs 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 Clinton advisers and allies said.
To those she did inform, Mrs Clinton was emphatic: She intended to "press on" with her campaign schedule.
She was optimistic 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.
In a phone interview with CNN's Anderson Cooper on Monday night, Mrs Clinton said she had kept her pneumonia diagnosis a secret because "I just didn't think it was going to be that big a deal".
But the manner in which Mrs Clinton's illness became public has revived concerns among supporters, and criticism among detractors, about her seemingly reflexive tendency to hunker down and hoard information, 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 e-mail server as secretary of state, and now threatens to make her look, again, as though she has something to hide.
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.
"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. "But there's also a combination of a natural desire for privacy and the fear that information will be politically misused."
Others were more blunt. "Antibiotics can take care of pneumonia. What's the cure for an unhealthy penchant for privacy that repeatedly creates unnecessary problems?" Mr David Axelrod, a former adviser to President Barack Obama, wrote on Twitter.
While Mr Trump has so far showed uncharacteristic restraint after her campaign announced she had pneumonia, he took Mrs Clinton's unexpected absence from public view as an opportunity to press his case with ferocity.
He has hurled himself into a new effort to reshape the presidential race, scrambling to allay voters' concerns about his temperament and put Mrs Clinton on the defensive over her critical comments about many of Mr Trump's supporters, whom she called a "basket of deplorables" at a fund-raiser last Friday. She later she said regretted the remarks after a fierce backlash.
Among Mr Trump's advisers, there is a sense of urgency. With eight weeks left in the race, Mr Trump may never again have such a window to make his argument to voters more or less uninterrupted.
On a conference call with top supporters on Monday, advisers to Mr Trump spoke of Mrs Clinton's turbulent stretch as a source of relief. For the first time in a while, they said, they were starting the week on offence.