The marriage of former first lady Rosalynn Carter, who died Sunday at 96, and former president Jimmy Carter evolved over more than 77 years from a stereotypical relationship of the 1950s to the point that she became her husband’s closest adviser and fiercest advocate in all matters of politics, public service, and life, particularly on the issue of mental health, says Carter biographer Randall Balmer, the John Phillips Professor in Religion.

By the time Jimmy and Rosalynn Carter campaigned at Dartmouth in the lead-up to his famous New Hampshire primary victory in 1976, her political savvy was well established, but it wasn’t always that way.

“In 1962, when Jimmy Carter decided on his 38th birthday to file for election in a county courthouse, he rolled out of bed and announced to Rosalynn that he was filing to run for the Georgia state senate,” Balmer says. “This was the first she’d heard anything about it.”

When the former president recounted that day in an interview for Balmer’s 2014 book, Redeemer: The Life of Jimmy Carter, he was embarrassed.

“When I talked to him about it, he actually blushed and he said, ‘I just can’t believe I did that,’ ” Balmer recalls.

The announcement in February that Jimmy Carter was receiving hospice care led to many retrospectives on the former president’s life. Jimmy Carter, now 99, has survived his life partner, and Rosalynn’s impact is becoming clearer.

From running the financial side of the Carter family peanut farm to tirelessly campaigning in her husband’s races for state senate, governor, and president to cofounding the Carter Center—one of the most activist presidential foundations in history—Rosalynn Carter was a true partner and a force to be reckoned with, Balmer says.

“It was a marriage of equals, there’s no question about that. In the end, the only person he fully trusted was Rosalynn,” Balmer says.

During the Carter presidency, Rosalynn became the first presidential spouse to have an office and a staff in the East Wing of the White House. She attended national security briefings and had a weekly lunch with the president to brief him on what she had learned in her travels about how his presidency was perceived, Balmer says.

And perhaps most significantly, she declared the agenda of the Office of the First Lady was to work for legislation to address mental health and the needs of the elderly, issues she continued to pursue with the Carter Center to the end of her public life.

During her time in the White House, she testified before a Senate subcommittee, becoming the first first lady since Eleanor Roosevelt to address a congressional panel, the Associated Press reported.

She was still working the issue in 2007, almost 30 years later, when she pushed Congress for improved insurance coverage for mental health, telling the panel, “Mental illnesses are diseases like any other. They can be diagnosed and treated, and the majority of people who have them can lead fulfilling lives, working, going to school, and being productive members of their community.”

Even the founding of the Carter Center in Atlanta—which is renowned for its work on mental health, public health, and disease eradication and its advocacy of election integrity, rule of law, and human rights around the globe—was driven by Rosalynn Carter, Balmer says.

After Carter’s defeat by President Ronald Reagan in the 1980 election, Rosalynn was distraught at the prospect that their public life was over.

“In one of our conversations, Mr. Carter told me that one of the reasons for the Carter Center, and one of the reasons he bounced back so quickly after that defeat, was that he was repeatedly assuring Rosalynn that they still had a life to live, and they still had things that they could do,” Balmer says.

“Carter said, ‘I began to believe it after a time. It was simply because I had to reassure her and try to pull her out of her funk after the 1980 defeat,’ ” Balmer says.

Reflecting on his time with Carter during research for the biography, Balmer observes, “Carter was a quiet man. It was kind of hard to get to know him in many ways, and I think Rosalynn really was his soulmate and most trusted confidante, perhaps truly the only one.”

Tim Kraft ’63, a key campaign aide during Carter’s 1976 presidential primary campaign who then became a high-ranking White House staffer, says Rosalynn was astute politically and a hard worker, traits that stemmed from her middle-class upbringing in rural Plains, Ga.

Kraft saw her in action in the fall of 1975, when she insisted on visiting four Congressional districts in Iowa as part of campaigning before the Iowa caucuses.

“Everywhere she went, she just made a very good impression. She had a set speech about growing up in Plains, working with Governor Carter. She could handle most political questions. She was just a natural charmer,” Kraft says.

And once in the White House, she continued to put work ahead of glamor.

“She insisted on her own staff. She wasn’t going to be overly concerned with decor and the social side of things. She wanted to do significant things in the field of mental health and set about getting a staff and office and capable people, and was very active,” Kraft says.

Those efforts helped put more of a spotlight on mental health, which often went unmentioned at the time.

“When she made that a part of the East Wing of the White House, it became a touchstone for people around the country and around the world,” Kraft says. “She just kindled something that resonated.”

And Kraft saw firsthand how close the Carters truly were when he and Jimmy Carter returned to Georgia from a campaign trip in 1975.

“He got off the plane and he’d say, ‘Timothy, where’s my wife?’ ” Kraft recalls. “That just sort of stuck with me.”