In July, President Obama stood on an outdoor stage before a crowd of 2,000 people at Los Angeles Trade Technical College.
The president had just begun a new campaign-style speech when a man in the crowd, standing less than 50 feet away, interrupted with loud cries. "Antichrist!" the man yelled. "You'll be destroyed!"
As the Secret Service moved in, Obama cracked a joke from the podium to keep things light. He had seen the man before, he said: "He needs to update his material."
Less than an hour later, however, off stage and surrounded again by security and staff members, the president was no longer laughing.
"That man would kill me," he told them flatly.
The moment, retold by a person with direct knowledge of the remark who asked not to be identified, was even more remarkable for its rarity.
Aides say that the president seldom discusses potential threats. His comment about the man, and its implications about the effectiveness of his bodyguards, offers a glimpse of the complex, intense relationship every president and his family have with the protectors who constantly surround them.
Proximity and dependence inevitably breed a personal, almost familial relationship with Secret Service agents, former protectees note, and one that relies, above all, on trust.
That trust was cracked in recent weeks as a string of security breaches revealed surprising lapses in protocol and in candor at the Secret Service.
This week, as the president accepted agency head Julia Pierson's resignation, White House officials suggested the breaking point was not that a man had jumped a fence and entered the White House last month, but that Pierson had withheld from Obama another breach: an armed security contractor had managed to ride in an elevator with the president.
Chosen to replace Pierson was a former head of the president's security detail, Joe Clancy, who had earned the family's confidence, one official said.
That appears to be key as the White House and Secret Service reset their relationship. First Lady Michelle Obama made it clear that she "intensely supported" Clancy, the official said, in a rare acknowledgment of the first lady inserting her opinion into official business.
Despite the signs of private frustration, the president and his aides have publicly defended the defenders. Obama has spoken only once about the Secret Service since the White House intrusion, saying last week that he was "grateful for all the sacrifices they make on my behalf and on my family's behalf."
White House spokesman Josh Earnest tread lightly all week, expressing no alarm about the president's safety, even as reporters pressed to see signs of outrage.
Obama and his family had to adjust to the ubiquity of men and women in dark suits and earpieces earlier and more quickly than many other politicians.
He first received protection in May 2007, less than three years removed from his low-key life as an Illinois state senator and amid of a rush of concern for the safety of a man drawing large crowds as potentially the first African American president.
After Obama was elected, the Secret Service noted a surge in threats against him. Conversations about his safety became commonplace.
Within a few months, the threats "came down to a level consistent with his predecessors, and they've stayed that way," Secret Service spokesman Ed Donovan said. Aides say that the president seems largely at ease with his safety.
Over time, the first family settled into a comfortable relationship with the agents who follow them, former aides and a former officer said.
In the hallway of a hotel one day during the campaign, Sasha Obama, then about 7, was spotted calling for the attention of her favorite agent. She confidently tumbled into a handstand as the agent caught her feet, according to two Obama staffers who watched. After the dismount, she skipped away, while the agent turned to the staffers and grinned.
"Babysitter with a gun," he said.
In his early days in the White House, it was those seasoned agents, many of them veterans of the George W. Bush White House, to whom Obama looked for guidance.
Obama once stopped in front of one of the formal rooms, hesitated, and then asked a Secret Service officer nearby if he was allowed to enter.
"Yes, sir," said the officer. "You can go wherever you want."
The opposite holds true outside the White House, and Obama and the first lady have sometimes chafed under the weight of the protection.
Michelle Obama has joked that the White House is a "really nice prison." Obama spoke fondly of what he recalls as his last "walk unencumbered," when his new agents agreed to hang back while he strolled briefly along the river in Austin, Texas, during the 2008 campaign.
"I have wistful memories of that walk," he told an audience this summer.
For first children, agents can be another trial of growing up, Anthony said. Lynda Bird Johnson Robb, daughter of Lyndon and Lady Bird Johnson, has often noted how uncomfortable dating was. Patti Davis openly resented her detail, suspecting, correctly, that her mother, Nancy Reagan, was using agents to find out whom Davis was seeing.
Agents often work with protectees for years, said Mickey Nelson, a former director of protective details for the president and vice president. But they take care to keep an arm's-length relationship.
They are advised not to initiate conversation. When updates are necessary, agents are told to keep them brief and to the point — for example, offering a quick notification of a traffic delay when driving.
"There shouldn't be idle conversation," Nelson said. "It should all be on a professional level."
Agents try to blend in and avoid fraternizing with the people they guard, one former aide said. A White House advisor describes it as an "intimate dance." The agent knows private details about the protectee's life — who calls, who cries, who yells — but is charged with remaining discreet.
"There's a closeness — but with the professional detachment," former Vice President Walter Mondale said.
Mondale, who notes that he was not regularly threatened, remembers the few times he was told of concerns. He was instructed to allow his agents to stay close as he walked through a crowd. They are trying to prevent a gunman from getting a clear shot, they told him.
"You've got to admire people who do that," he said.
Still, Mondale and other protectees expressed shock at the lapses that have emerged in recent weeks and note that it will take time before the image of the agency is restored.
As for Obama's wish to roam more freely, that will only be achieved when he's out of office — although still under the watchful eye of agents. Presidents are assigned a detail for life.