In the weeks and months before President Biden’s politically devastating performance on the debate stage in Atlanta, several current and former officials and others who encountered him behind closed doors noticed that he increasingly appeared confused or listless, or would lose the thread of conversations.
Like many people his age, Mr. Biden, 81, has long experienced instances in which he mangled a sentence, forgot a name or mixed up a few facts, even though he could be sharp and engaged most of the time. But in interviews, people in the room with him more recently said that the lapses seemed to be growing more frequent, more pronounced and more worrisome.
The uncomfortable occurrences were not predictable, but seemed more likely when he was in a large crowd or tired after a particularly bruising schedule. In the 23 days leading up to the debate against former President Donald J. Trump, Mr. Biden jetted across the Atlantic Ocean twice for meetings with foreign leaders and then flew from Italy to California for a splashy fund-raiser, maintaining a grueling pace that exhausted even much younger aides.
Mr. Biden was drained enough from the back-to-back trips to Europe that his team cut his planned debate preparation by two days so he could rest at his house in Rehoboth Beach, Del., before joining advisers at Camp David for rehearsals. The preparations, which took place over six days, never started before 11 a.m. and Mr. Biden was given time for an afternoon nap each day, according to a person familiar with the process.
Referring to the start time, Andrew Bates, a White House spokesman, said “the president was working well before then, after exercising.”
The recent moments of disorientation generated concern among advisers and allies alike. He seemed confused at points during a D-Day anniversary ceremony in France on June 6. The next day, he misstated the purpose of a new tranche of military aid to Ukraine when meeting with its president.
On June 10, he appeared to freeze up at an early celebration of the Juneteenth holiday. On June 18, his soft-spoken tone and brief struggle to summon the name of his homeland security secretary at an immigration event unnerved some of his allies at the event, who traded alarmed looks and later described themselves as “shaken up,” as one put it. Mr. Biden recovered, and named Alejandro N. Mayorkas.
He is certainly not that way all the time. In the days since the debate debacle, aides and others who encountered him, including foreign officials, described him as being in good shape — alert, coherent and capable, engaged in complicated and important discussions and managing volatile crises. They cited example after example in cases where critical national security issues were on the line.
Aides present in the Situation Room the night that Iran hurled a barrage of missiles and drones at Israel portrayed a president in commanding form, lecturing Prime Minister Benjamin Netanyahu by phone to avoid a retaliatory escalation that would have inflamed the Middle East. “Let me be crystal clear,” Mr. Biden said. “If you launch a big attack on Iran, you’re on your own.”
Mr. Netanyahu pushed back hard, citing the need to respond in kind to deter future attacks. “You do this,” Mr. Biden said forcefully, “and I’m out.” Ultimately, the aides noted, Mr. Netanyahu scaled back his response.
This account is based on interviews with current and former White House aides, political advisers, administration officials, foreign diplomats, domestic allies and financial donors who saw Mr. Biden in the last few weeks, sometimes just briefly, sometimes for more extended periods. In most cases, they spoke on condition of anonymity because of the delicacy of the matter.
White House officials have said the president is in excellent shape and that his debate performance, while disappointing, was an aberration. Kevin C. O’Connor, the White House physician, said as recently as February that despite minor ailments like sleep apnea and peripheral neuropathy in his feet, the president was “fit for duty.” He said tests had turned up “no findings which would be consistent with” Parkinson’s disease. The White House has declined to make Dr. O’Connor available for questions and did not respond to detailed health questions from The New York Times earlier this year.
Andrew Bates, a White House spokesman, said Tuesday that Dr. O’Connor had found no reason to re-evaluate Mr. Biden for Parkinson’s disease and that he showed no signs of Parkinson’s and had never taken Levodopa or other drugs for that condition.
Aides to Mr. Biden responded to questions for this story by asking several senior advisers to describe their interactions with Mr. Biden.
“He’s inquisitive. Focused. He remembers. He’s sharp,” said Neera Tanden, the president’s domestic policy adviser. In briefings, she said, “he will ask you a tough question and he will say, ‘How does this relate to an average person?’ And if you haven’t thought of that in that time, you have to come back to him.”
Elizabeth Sherwood-Randall, the president’s homeland security adviser, recounted a June 17 terrorism briefing for Mr. Biden in the Situation Room in which he “digested an immense amount of information” and asked questions that were “probing and insightful.” She acknowledged that Mr. Biden’s debate performance had been different. “It doesn’t reflect the experience I have with him on a daily basis,” she said.
But by many accounts, as evidenced by video footage, observation and interviews, Mr. Biden is not the same today as he was even when he took office 3½ years ago. The White House regularly releases corrected transcripts of his remarks, in which he frequently mixes up places, people or dates. The administration did so in the days after the debate, when Mr. Biden mixed up the countries of France and Italy when talking about war veterans at an East Hampton fund-raiser.
Last week’s debate prompted some around him to express concern that the decline had accelerated lately. Several advisers and current and former administration officials who see Mr. Biden regularly but not every day or week said they were stunned by his debate performance because it was the worst they had ever seen him.
“You don’t have to be sitting in an Oval Office meeting with Joe Biden to recognize there’s been a slowdown in the past two years. There’s a visible difference,” said Douglas Brinkley, a presidential historian. “I’ve been amazed on one hand,” said Mr. Brinkley, who has not seen the president in person in a year. “The president can zip around the country like he does. But the White House may only be showing the Biden they want us to see.”
Mr. Trump, 78, has also shown signs of slipping over the years since he was first elected to the White House. He often confuses names and details and makes statements that are incoherent. He maintains a lighter public schedule than Mr. Biden, does not exercise and repeatedly appeared to fall asleep in the middle of his recent hush money trial. His campaign has released only a three-paragraph health summary. Voters have expressed concern about his age as well, but not to the same degree as Mr. Biden’s.
Mr. Trump has seized on Mr. Biden’s debate performance and called his own often confusing and fact-free appearance that night the “greatest debate performance” in the history of presidential campaigns.
The picture that emerges from recent interviews about Mr. Biden is one of a president under stress — hardly unusual — as he tried to juggle nervous international partners, a recalcitrant ally whose continued war against Hamas was creating yet another threat to a second term and a family crisis with his own son, who was convicted of criminal charges that could send him to prison.
By necessity, it is an incomplete picture. As Mr. Biden has aged, the White House has limited his encounters with reporters. While he frequently stops for a couple minutes to answer a question or two, as of Sunday, Mr. Biden had granted fewer interviews than any president of the modern era and fewer news conferences than any president since Ronald Reagan, according to statistics compiled by Martha Kumar, a longtime scholar of presidential communication.
On the occasions that Mr. Biden has chosen to speak with reporters on short notice, it has not always gone well. In February, he angrily hit back against a special counsel’s report on his handling of classified documents, in which the special counsel, Robert K. Hur, characterized the president as a “well-meaning, elderly man with a poor memory.” The furious president defended himself and his memory to reporters but referred to President Abdel Fattah el-Sisi of Egypt as the “president of Mexico” in the process. On Monday, House Republicans sued the Biden administration in an attempt to procure audio of Mr. Biden’s interviews with Mr. Hur.
But those 23 days before Mr. Biden met Mr. Trump on the television stage in Atlanta may be viewed by historians as the most critical three weeks in a consequential presidency, as the president faced an opponent he not only loathed, but viewed as an existential threat to American democracy. Were the wandering, inconclusive thoughts broadcast live to more than 50 million viewers just a bad night, a product of the exhausting month, or something larger? Had he not been crisscrossing the globe so frequently — including leaving Italy for a trip spanning nine time zones to a fund-raiser in Los Angeles — would it have made a difference?
Mr. Biden’s trips to Europe were marked by moments of sharpness in important meetings — including a complex session on diverting income from Russian assets to aid Ukraine — mixed with occasional blank-stared confusion, according to people who met with him. At some points, he seemed perfectly on top of his game, at others a little lost.
In Normandy, he met former soldiers brought to France by a veterans’ group. One American who attended said Mr. Biden’s eyes seemed glazed and it appeared that people had to lead him. During the later ceremony, the president turned away from the U.S. flag when “Taps” was played instead of facing it, possibly to not turn his back to the veterans. Jill Biden, President Emmanuel Macron of France and Mr. Macron’s wife then followed suit.
There was an awkward moment when Mr. Macron made sure the president got safely down the ramp, then came back up to shake all the veterans’ hands. Mr. Biden had been expected to stay for the handshakes.
During a meeting the next day with President Volodymyr Zelensky of Ukraine, Mr. Biden spoke so softly it was almost impossible to hear and said a new burst of aid was meant to reconstruct the country’s electric grid when it was not.
But when it came time for the president’s own speech on D-Day, he delivered it forcefully and clearly, gathering momentum and ending on a vigorous note. It was a reminder that, much like during the State of the Union address earlier in the year, he often rises to big occasions and once he gets the rhythm of a speech, adrenaline appears to kick in.
Age was a running theme throughout the visit to France as the president honored American veterans who were near the century mark.
“Age is just a number,” Hilbert Margol, a 100-year-old who served in World War II, recalled telling Mr. Biden.
“You’re right,” Mr. Biden agreed.
Bill Casassa, 98, who was also honored at the Normandy ceremony and supports Mr. Trump, said he came away with the impression that Mr. Biden was infirm. “He did not appear any different to me in person than he does on television — and that is as a person who is fragile and not really in charge,” Mr. Casassa said.
Another veteran, Marvin E. Gilmore Jr., on the other hand, said he came away with newfound respect for Mr. Biden’s energy. “He greeted me very openly, very warmly and very, very, alert,” said Mr. Gilmore, who plans to vote for him. “There was nothing I saw in him that said he was an old man — and I am 99, three months from being 100.”
After several days in France, Mr. Biden flew home briefly and dealt with the family crisis of his son’s conviction. He hosted an early concert marking the Juneteenth holiday where he was spotted standing stiffly during a musical performance. One person who sat close to the president said that he had a “dazed and confused” expression during much of the event. This person said Mr. Biden had shown a “sharp decline” since a meeting only weeks earlier.
After just a couple days at home, Mr. Biden turned around and flew back to Europe, this time to Italy for a summit of the Group of 7 leaders. Throughout the meetings, the pattern was the same, according to senior officials who attended.
Mr. Biden, one said, appeared “quite sharp in the meetings,” and was well prepared. He articulated American views. He appeared on his game at a news conference with Mr. Zelensky. But at one point Mr. Biden appeared to wander off from the group of leaders to talk to paratroopers and the Italian prime minister, Giorgia Meloni, came up behind him, and gently brought him back. A clip of the event that went viral had been edited to make it appear Mr. Biden had just walked away. In fact, he was greeting a paratrooper. But the image suggested he needed guidance from his host.
A senior European official who was present said that there had been a noticeable decline in Mr. Biden’s physical state since the previous fall and that the Europeans had been “shocked” by what they saw. The president at times appeared “out of it,” the official said, and it was difficult to engage him in conversation while he was walking.
Ms. Meloni and the other leaders were acutely sensitive to Mr. Biden’s physical condition, discussing it privately among themselves, and they tried to avoid embarrassing him by slowing their own pace while walking with the president. When they worried that he did not seem poised and cameras were around, they closed ranks around him physically to shield him while he collected himself, the official said.
Two administration officials who traveled with Mr. Biden to Italy said the hotel where the Group of 7 summit was taking place was a warren of confusing corridors filled with 25 world leaders and their security details. But they said Mr. Biden was articulate and sharp through hours of meetings.
Asked if one could imagine putting Mr. Biden into the same room with President Vladimir V. Putin of Russia today, a former U.S. official who had helped prepare for the trip went silent for a while, then said, “I just don’t know.” A former senior European official answered the same question by saying flatly, “No.”
Some White House officials adamantly rejected the suggestion of a president not up to handling tough foreign counterparts and told the story of the night Iran attacked Israel in April. Mr. Biden and his top national security officials were in the Situation Room for hours, bracing for the attack, which came around midnight. Biden was updated in real time as the forces he ordered into the region began shooting down Iranian missiles and drones. He peppered leaders with questions throughout the response.
After it was over, and almost all of the missiles and drones had been shot down, Mr. Biden called Mr. Netanyahu to persuade him not to escalate. “Take the win,” Mr. Biden told the prime minister, without reading from a script or extensive notes, according to two people in the room. In the end, Mr. Netanyahu opted for a much smaller and proportionate response that effectively ended the hostilities.
Mr. Biden left Italy to fly directly to Los Angeles for a star-studded fund-raiser with Hollywood celebrities and former President Barack Obama, stopping back in Washington just long enough for Air Force One to be refueled. Aides pointed to the trip as an example of remarkable stamina for an octogenarian — or for anyone, for that matter.
But Mr. Biden appeared tired during a 40-minute discussion onstage at the event, seated between Jimmy Kimmel and Mr. Obama. A few times, the president stumbled over his words, and when the other men were speaking, Mr. Biden often stared into space, his mouth slightly open, like he would later do at the debate.
Two days after finally returning to the White House, Mr. Biden invited members of Congress, former administration officials and leading immigration experts to the White House to celebrate action taken under Mr. Obama to spare young undocumented immigrants, known as Dreamers, from deportation.
Two people with a clear view of Mr. Biden said his quiet, soft-spoken mumbling and occasional fumbling over the right words despite reading from a teleprompter left some in attendance concerned over his condition. He momentarily appeared unable to say the name of Mr. Mayorkas, his homeland security secretary, before recovering, leaving some in the audience jarred.
“Thanks to all the members of the Congress and Homeland Security Secretary — I — I’m not sure I’m going to introduce you all the way,” said Mr. Biden, who has contended with a stutter since childhood. “But all kidding aside, Secretary Mayorkas.”
While many were celebratory at the event, in which Mr. Biden announced a new program to grant relief to roughly 500,000 undocumented immigrants, some attendees shared their concerns about Mr. Biden’s condition with each other. “People were not feeling great,” one person said. Another person hoped it was just a “one-off” bad moment before Mr. Biden’s forthcoming debate.
Since the debate, Mr. Biden has tried to demonstrate that his trouble articulating himself that evening was not indicative of a larger problem. He gave a robust speech at a campaign rally the next day and attended a string of fund-raisers where he hoped to reassure nervous donors.
“He gave a strong speech, he didn’t stumble or mumble or look confused in any way,” said Judith Hope, the former chair of the New York State Democratic Party, who attended a fund-raiser in East Hampton on Saturday. “He was his old Uncle Joe self.”
Ms. Hope attributed the president’s debate troubles to his demanding schedule. “Are you aware of where he has been in the past seven days?” she said, raising her voice. “He continues to keep up a schedule that I could never dream of doing, that would totally defeat a younger person,” she added. “I think we need to examine our expectations.”
Reporting was contributed by Michael D. Shear and Erica L. Green from Washington; Matina Stevis-Gridneff from Brussels; Catherine Porter and Roger Cohen from Paris; Sarah Maslin Nir and Steven Erlanger from Berlin; and Andrew E. Kramer from Kyiv.