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(WASHINGTON) — In the tumultuous weeks since President Joe Biden’s faltering debate performance, the 81-year-old commander-in-chief has resisted calls from within his own party to end his reelection campaign, often relying on assurances from his medical staff to rebuff those who question his fitness for office.

This week, in an interview with BET, Biden suggested for the first time that he would consider dropping out of the presidential race if there was “some medical condition that emerged … if the doctors came to me, said, ‘You got this problem and that problem.'”

The person who would carry that heavy burden is a media-shy physician who Biden warmly refers to as “Doc”: the 58-year-old head of the White House medical unit, Dr. Kevin O’Connor.

A retired Army surgeon who served tours with special operations forces in Iraq and Afghanistan, O’Connor has spent more than a decade caring for Biden. One former White House aide described the osteopath as being “like family” to the Bidens.

And now, with the aging president’s health front and center in the 2024 race — and with him facing a second COVID-19 diagnosis since taking office — O’Connor seems poised to remain in the spotlight.

In nearly a dozen interviews, current and former colleagues praised O’Connor as a top-tier clinician and an “honest doctor” whose deep bond with his high-profile patient makes him uniquely qualified to deliver unwelcome prognoses, if warranted.

“If [O’Connor] felt there was a problem for the country, he would tell the president and he would tell the American people,” said Retired Army Colonel Dr. John Holcomb, a longtime friend. “That would be a hard decision. But it would be the right thing to do, and [O’Connor] would do it.”

But as the president’s public gaffes continue, a chorus of critics, allies and medical professionals have questioned his mental acuity — and his medical staff’s reluctance to divulge more information about his health.

Dr. Lawrence Mohr, the White House physician to Presidents Ronald Reagan and George H.W. Bush, told ABC News that based on what he has seen publicly, “I don’t think there’s any question that the president should undergo a test of cognitive function, and he should do it very quickly.”

House Republicans have also suggested that O’Connor’s “connections with the Biden family” compromise his ability to “provide accurate and independent reviews of the president’s fitness to serve.”

O’Connor did not respond to a request to be interviewed. But several people close to him said he has grown irritated in recent weeks amid scrutiny of his clinical decisions and character. One person who recently spoke with O’Connor said the newfound attention is “bugging him.”

O’Connor rarely makes public appearances, preferring instead to communicate news about the president’s health in written statements. But in a podcast interview earlier this year, the physician described himself as “apolitical.”

“We don’t serve the president; we serve the presidency. That is sacrosanct,” he said on the podcast WarDocs. “We’re not here for a man, we’re here for the office … [President Biden] knows that. He wants it that way.”

Andrew Bates, a White House spokesperson, described O’Connor as “a world class medical professional” whose “unique expertise is sought across the medical community, in which he is respected for his candor, attention to detail, and work ethic.”

‘Brotherly trust’

A New Jersey-bred high school wrestler, O’Connor served for 22 years in the Army, where he cut his teeth jumping out of airplanes with the 82nd Airborne Division and later as a medic with special operations units. He was “one of the very first Americans to go into Afghanistan” during the early days of the War on Terror, according to Dr. Frank Butler, a retired Navy surgeon.

As he rose through the ranks, O’Connor played a “pioneering role” in overhauling the U.S. military’s battlefield trauma care, known as the Tactical Combat Casualty Care, and was an early advocate of the use of ketamine to treat severe depression in servicemembers and veterans, Butler said.

In 2006, during his time as a hospital administrator at Fort Carson in Colorado, O’Connor was asked to consult about a patient suffering from back pain. The patient, O’Connor later learned, was President George W. Bush — and his treatment set the course for a career pivot to the White House.

“I beat him up pretty good,” O’Connor recalled in the podcast interview, regarding his treatment of Bush’s back issue. After that initial treatment, “[Bush] started calling me ‘bone-crusher’ … and over the course of time that morphed into ‘bone-cracker'” and later, simply to “‘cracker,’ which was unfortunate,” O’Connor said.

O’Connor joined the White House medical unit full-time later that year. When the Obama administration swept into office in 2009, O’Connor said he “fell into” the role of primary physician for then-Vice President Biden.

The two men grew close when Biden asked O’Connor to consult on end-of-life care for his mother, who passed away in 2010. Their bond deepened, friends said, when Biden’s son Beau Biden was later diagnosed with cancer.

Through those trying moments, the two men forged a “brotherly trust” that remains in place today, according to a current administration official who worked for Biden during the Obama administration.

In an October 2016 email inviting several members of the Biden family to a party Biden hosted for O’Connor’s retirement from the Army, O’Connor wrote that “a retirement ceremony really has little to do with the retiree — it’s for their family.”

“I can never imagine a day when any of you call and I don’t pick up the phone with a smile,” he wrote, before signing the message, “Love, Kevin.”

After Biden left office in 2017, O’Connor remained his physician — the only difference being “that [Biden] got a bill and he drove himself [to appointments],” O’Connor said on the WarDocs podcast.

O’Connor also continued to treat and provide consultations for members of Biden’s family, including his son, Hunter Biden, and Hunter Biden’s daughters, according to emails leaked online from Hunter Biden’s laptop hard drive.

When Biden was elected president in 2020, O’Connor was summoned back to the White House as the physician to the oldest president in American history. In the intervening years, O’Connor has penned extensive annual reports on the president’s health — most recently in February, when he declared that Biden “continues to be fit for duty.”

But many Americans disagree. In last week’s ABC News/Washington Post/Ipsos poll, Trump leads Biden by 30 percentage points, 44% to 14%, in being seen as having the mental sharpness it takes to serve effectively as president.

Even so, O’Connor has committed to being forthright with the president about any troubling medical observations.

“You’ve got to tell them what they need to hear,” O’Connor said on the WarDocs podcast in January. “We don’t candy-coat things in medicine.”

‘I would love to live in anonymity’

Despite his high-profile role, O’Connor has made a concerted effort to stay under the radar. Where past White House physicians have, under certain circumstances, taken questions from the media, O’Connor said on the WarDocs podcast that he laments “the press stuff.”

“I like to not deal with that more than I have to,” he said. “I’m very thorough and very honest and very forthcoming in writing every time [Biden has] been sick … but still they want more.”

Republicans in Congress have suggested that O’Connor’s close ties with Biden might undermine his objectivity in delivering updates on the president’s health. In a letter to O’Connor last week, House Oversight Committee Chairman James Comer highlighted O’Connor’s apparent involvement with James Biden, the president’s brother, in an ill-fated business endeavor dating back to 2017.

James Biden, in an interview with committee investigators earlier this year, said O’Connor introduced him to a group of individuals with expertise in providing PTSD care to servicemembers as part of his role in Americore, a hospital system looking to expand access to healthcare access in rural areas.

“The Oversight Committee is concerned your medical assessments have been influenced by your private business endeavors with the Biden family,” Comer wrote in the letter.

Paul Fishman, an attorney for James Biden, acknowledged in a statement that “Jim sought his advice on best practices” — but insisted that “O’Connor was not in business with Jim” and that O’Connor was not paid for brokering the meeting.

Ian Sams, a White House spokesperson, called Comer’s overture “absolutely ridiculous and insulting.”

Republicans’ scrutiny of O’Connor and the broader discourse about Biden’s mental health has drawn the behind-the-scenes West Wing fixture into the open, despite his protestations.

“My goal right now in this job is [that] I hope nobody has any memory of me whatsoever,” he said on the WarDocs podcast in January. “I would love to live in anonymity.”

But few people have more access to the president, and fewer still have the training to evaluate his fitness for duty — a point O’Connor himself has acknowledged as a crucial part of his role. His office sits on the ground floor of the executive residence, directly across from the president’s personal elevator.

“[The president] literally has to pass me at least twice a day, usually more than that, to and from his way to the Oval Office,” he told a group of medical students earlier this year. “I have always viewed the most important part of my day as, ‘Good morning, Mr. President.'”

Experts point out that O’Connor is limited in what he can say publicly about Biden’s health. The same doctor-patient confidentiality that applies to every American, through the Health Insurance Portability and Accountability Act, or HIPAA, also applies to the president.

“It’s not the doctor’s responsibility — or even the doctor’s authority — to make statements about the medical conditions about the president,” said Dr. Mohr, the former physician to Reagan and George H.W. Bush. “That’s the president’s responsibility.”

“It’s never the doctor’s prerogative to make statements without the president’s permission,” Mohr said.

Dr. Philip Volpe, a retired major general and O’Connor’s longtime mentor, told ABC News that he shared this advice with the president’s physician last week: “Be a good doc, do the right thing, and tell the truth.”

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