ATLANTA — When Jimmy Carter entered hospice care at his Georgia home last year, his family and friends thought he had only days to live. More than 19 months later, he is set to celebrate his 100th birthday Tuesday, the first president in American history to hit the centennial mark.

The last chapter of Carter’s already remarkable life story is turning out to be one of astonishing resilience. The peanut-farmer-turned-global-statesman has over the years beaten brain cancer, bounced back from a broken hip and outlived his political adversaries. And now he is setting a record for presidential durability that may be hard to break.

Though frail and generally confined to his modest ranch house in Plains, Ga., Carter has not only refused to surrender to the inevitability of time, he has perked up in recent months, according to family members. He has become a little more engaged again, telling his children and grandchildren that he has a new milestone he wants to reach — not his birthday, which he professes not to care that much about, but Election Day, so he can vote for Vice President Kamala Harris.

“It’s a gift,” Josh Carter, one of his grandsons, said of the past few months. “It’s a gift that I didn’t know we were going to get.”

Carter had already surpassed all of his predecessors to become the longest-living president, but some of those who have experienced his stubborn irascibility over the decades said they were not surprised that he is approaching his second century.

“That’s Jimmy,” said Gerald Rafshoon, his White House communications director and longtime friend. “It’s almost like his whole life has been to go against the norm. Tell him he can’t do something, just tell him that, and you’re bound to see the determination.”

Carter’s hometown, Plains, the blink-and-you’ll-miss-it speck on the map in southwest Georgia with barely 500 residents, is celebrating his birthday with a flyover of military jets, a naturalization ceremony for 100 new citizens and a concert. Supporters already held a lively concert last month at Atlanta’s Fox Theater to be televised Tuesday, including performances by the B-52s, BeBe Winans and others, along with videotaped tributes from most of the other presidents.

Carter was not able to attend personally. He has become severely diminished physically. There are days when his grandchildren and great-grandchildren travel to Plains only to be told that he is not able to see them.

The death last year of his wife, former first lady Rosalynn Carter, was crushing and disorienting, relatives said. After 77 years of marriage, many around him assumed he would follow her soon.

“When she passed, we all frankly thought that he wouldn’t be much longer,” said Jason Carter, another grandson and the board chair of the Carter Center, the philanthropic institution founded by the former president and first lady. “And I think he had a real low period for awhile. But these last few months, he’s really gotten reengaged with the world.”

The former president listens to music, including old standbys like Bob Dylan and the Allman Brothers Band. His favorite song is Garth Brooks’ “Unanswered Prayers.” He inquires about the work being done at the Carter Center and shares his opinions about the state of the Atlanta Braves. Ronald Acuña Jr.’s season-ending knee injury was a source of frustration.

He has followed the presidential election. He considers President Joe Biden a friend as well as a political ally, remembering how Biden as a young senator from Delaware had been among the earliest national Democrats to endorse his 1976 presidential candidacy.

Biden’s decision to end his reelection bid in July engendered a measure of pride and respect from Carter, Jason Carter said. The former president’s work with election-monitoring and nurturing democracies had taught him how rare it was for a leader to choose to surrender power for the sake of his party and his country.

“That’s a big — historically big — deal,” Jason Carter said. “Just like the rest of us, he couldn’t believe what we were watching because it was so unprecedented, and I think that was really affecting for him as well.”

The Carter family’s support of Harris stems in part from its staunch disapproval of former President Donald Trump. Trump has “a meanness and a darkness” that the family views as the antithesis of Carter’s philosophy, Jason Carter said.

Not surprisingly, Trump was the only former president not asked to send a video tribute to the Atlanta concert. Instead, he has been using Carter as a punchline on the campaign trail to mock Biden before the incumbent president left the race. “He makes Jimmy Carter look like a genius by comparison,” Trump said at a rally last summer.

Of course, Trump makes Carter look popular by comparison. In a Gallup poll last year, 57% of Americans retrospectively approved of Carter’s presidency compared with only 46% who approved of Trump’s.

In part, that may stem from the revisionist wave of nostalgia since Carter went into hospice. Once seen as a failed president who lost reelection only to become a globally admired humanitarian after leaving the White House, he has benefited from a reevaluation in the last 19 months.

As he reached his 80s and 90s, Carter became defined by his vigor and his defiance of the toll of aging. He published a memoir at age 90 and only moderately reduced his role at the Carter Center. He continued teaching at Emory University in Atlanta and routinely taught Sunday school at Maranatha Baptist Church in Plains.

At the Atlanta concert celebration last month, Monica Pearson, a longtime television news anchor in Atlanta, recalled once telling Carter that “90 is the new 60 — and I was absolutely right!”

Eventually, though, that resolve to keep active could look to family and caretakers an awful lot like stubbornness, showing up to teach Sunday school when everyone advised against it or helping build houses with Habitat for Humanity while bruised and bloodied after a fall.

The country witnessed that gritty defiance of limitations last November when Carter traveled to Atlanta for his wife’s memorial service.

“I don’t know what keeps him going,” Jason Carter said. “I think he doesn’t know how to give up on anything.” But he added that he worried that his bedbound grandfather was no longer having new experiences. “He’s so physically diminished,” he said. “I just worry that he’s not enjoying himself.”

Josh Carter said that when he visits, he is not seeing a president or an acclaimed humanitarian. “When I go back to Plains, he’s my grandfather” — the same one who took him into his wood shop and instilled in him a passion for woodworking.

The former president gave Josh everything in his wood shop on two conditions: that he use it, and that he start using it right away, not wait until after his grandfather’s death. He complied, using his grandfather’s tools to build a cabinet celebrating his grandparents’ 75th wedding anniversary.

Carter’s children and their spouses — including his sons Jeff and Chip and daughter Amy — have been the most directly involved in his care and send reports on his condition to the broader family.

“The caregiving side of this takes a toll, as it would in any family,” Jason Carter said. “All of us, I think, are surprised to see that he’s still going.”

“You know,” he added, “he may very well be immortal.”