ATLANTA — Jimmy Carter, already the longest-lived U.S. president in history, celebrated his 98th birthday Saturday with family and friends in Plains, the tiny Georgia town where he and his wife, Rosalyn, 95, were born in between World War I and the Great Depression.

The latest milestone for the 39th president is that the Carter Center, which the Carters co-founded after one term in the White House, celebrates 40 years of promoting democracy and conflict resolution, election monitoring and improving health care in countries that are developing.

Jason Carter, the former president’s grandson who now chairs the board of the Carter Center, described his grandfather, an outspoken Christian, as content with his life and legacy.

“He’s looking at his 98th birthday with faith in God’s plan for him,” said the younger Carter, 47, “and it’s just a wonderful blessing for all of us personally to know that he’s at peace and happy where he was.” and where he is going.’

Carter Center executives said the former president, who survived a cancer diagnosis in 2015 and a serious fall at home in 2019, was already enjoying reading congratulatory messages from well-wishers around the world via social media and the center’s website. But Jason Carter said what his grandfather looks forward to most is a simple day that includes watching his favorite Major League Baseball team, the Atlanta Braves, on TV.

“He’s still 100% with it, even though the day-to-day life is a lot harder now,” Jason Carter said. “But I guarantee one thing. He will be watching all the Braves games this weekend.”

James Earl Carter Jr. won the 1976 presidential election after starting the campaign as a little-known one-term governor of Georgia. His surprise performance at the Iowa caucuses made the small Midwestern state the epicenter of presidential politics. Carter went on to defeat President Gerald Ford in the general election, largely because he swept the South before his home region swung heavily to the Republicans.

A graduate of the Naval Academy, a naval officer and a peanut farmer, Carter won in no small part by promising to never lie to voters weary of the Vietnam War and the Watergate scandal that led to Richard Nixon’s resignation as president in in 1974. Four years later, after failing to curb inflation and appease voter anger over American hostages being held in Iran, Carter lost 44 states to Ronald Reagan. He returned home to Georgia in 1981 at the age of 56.

The former first couple began planning The Carter Center almost immediately. It opened in Atlanta in 1982 as the former president’s first venture of its kind. Stated mission: To promote peace, human rights and health worldwide. Carter won the Nobel Peace Prize in 2002. He traveled to various countries in his 80s and 90s, and he officially stepped down only in 2020.

Since opening, the center has observed elections in 113 countries, CEO Paige Alexander said, and Carter has also acted individually as a mediator in many countries. The Carter Center’s efforts have nearly eradicated the guinea worm, a parasite that spreads through unclean drinking water and causes pain in humans. Rosalyn Carter led programs aimed at reducing the stigma associated with mental illness.

“He’s enjoying his retirement,” said Alexandra, who took over her role in 2020, around the time Jason Carter replaced his grandfather. But “he spends a lot of time thinking about the projects he’s started and the projects we’re continuing.”

Alexander called the Guinea worm eradication effort a highlight. Carter set the target in 1986 when there were about 3.5 million cases annually in 21 countries, with a concentration in sub-Saharan Africa. So far this year, Alexander said, six cases are known in two countries.

In 2019, Carter used his final annual address at the center to lament that he had been largely silent on climate change since his presidency. Jason Carter said the center’s management is still exploring ways to deal with the climate crisis. But he did not offer a timetable. “We’re not going to duplicate other effective efforts,” Carter said, explaining that one of the center’s strategic principles is to prioritize cases and places that other human rights organizations haven’t.

In terms of elections and democracy, perhaps the most unpredictable twist is that Jimmy Carter lived to see the center shift its efforts to the domestic front. The center now has programs to combat mistrust of the democratic process in the United States. Carter Center staff have been monitoring the 2020 U.S. presidential election tally in Georgia after then-President Donald Trump said the result was rigged. Numerous recounts of votes in Georgia and other states confirmed the legitimacy of Joe Biden’s victory.

“Certainly, we never thought we’d be coming home to do democracy and resolve conflicts around our elections,” Jason Carter said. “(But) we couldn’t be this incredible organization for democracy and human rights abroad without making sure that we add our voice and our expertise … in the U.S.”

Ahead of the US midterm elections, the center asked candidates — regardless of party — to sign a number of principles for fair elections, including a commitment to a peaceful transfer of power. Among those who have signed the pledge are Georgia Gov. Brian Kemp, a Republican, and his Democratic challenger, Stacey Abrams.

Carter himself largely withdrew from politics. For years after his defeat in 1980, Democrats stayed away from him. It has enjoyed a resurgence in recent election cycles, attracting visits from several Democratic presidential candidates in 2020 and in 2021 from President Joe Biden, who in 1976 was the first U.S. senator to endorse Carter for the presidency. With inflation now at its highest level since the late 1970s and early 1980s, some Republicans are once again citing Carter as a line of attack against Biden and the Democrats.

Jason Carter said the former president reads and watches the news daily, and sometimes takes calls and visits from political figures. But, he added, the former president is not expected to appear publicly to endorse any candidates until November.

“His people that he feels like the closest connection to are the people in the Plains and his church and other places,” Jason Carter said. “But, you know, his partner #1, #2, and #3 is my grandmother, right? He outlived his friends and so many of his advisors and people he had accomplished so much with in the past, but they were never alone because they were always with each other.”