Some two decades after leaving the White House, Rosalynn Carter reflected on the criticism she generated for expanding the role of a first lady. “You can’t let it stop you,” she told an interviewer. “I didn’t let it stop me.” She had greater ambitions than simply throwing state dinners, she explained, and she paved the way for a new, more enduring view of how a presidential spouse could make a difference. “The first lady role has changed,” she observed. “I don’t think there will ever be another first lady who will be just a hostess and pour tea.” If that is true, Mrs. Carter will have been one of the primary reasons. While she spent only four years in the White House, she transformed the unelected, unpaid, and sometimes unappreciated position of first lady in ways that reverberate to this day. By the time she died at age 96 on Sunday at her home in Plains, Ga., she had long since dropped out of public view, but every one of her successors knew how important she was in shaping the role they inherited.

“We have Rosalynn Carter to thank for helping to expand and formalize the modern first lady’s office, a structure that is largely still in place to this day,” said Anita B. McBride, who served as chief of staff to Laura Bush when she was first lady — a staff job that itself has its origins in Mrs. Carter’s era. “It was a time in the country of profound change for women, and she wanted to seize the opportunities before her.”

Mrs. Carter never gained the international stature of Eleanor Roosevelt nor reached the political heights of Hillary Rodham Clinton, but she served as a full collaborator to her husband, former President Jimmy Carter. “Rosalynn was my equal partner in everything I ever accomplished,” her husband said in a statement on Sunday.

“She overcame shyness and became as good as or a better politician than he was,” she said. “There is no doubt he trusted her and her judgment.”

While modest and low-key, Mrs. Carter was a shrewd judge of character and politics, offering advice throughout her husband’s time in the White House from 1977 to 1981, most notably by inspiring and assisting his landmark Camp David meetings that brokered peace between Israel and Egypt.

“Eleanor set a new standard for the role. Lady Bird Johnson and Betty Ford were both groundbreakers and activists in their own way, leaving impressively lasting legacies. But Rosalynn, from the time she was first lady of Georgia to first lady of the land, took the activist model to a new level,“.

Mrs. Carter pushed the boundaries that had constrained most of her predecessors. She established a formal Office of the First Lady complete with an 18-person staff in the East Wing of the White House — “I had to go out the back door at first until people got used to having it there,” she told Melanne Verveer, who was Mrs. Clinton’s chief of staff — and she stunned traditionalists by attending cabinet meetings and national security briefings. She had officially scheduled weekly lunches with her husband to discuss policy issues, she traveled overseas solo to represent him and she testified before Congress.

“I would put Rosalynn Carter in the category of activist first lady,” said Ms. Verveer.

Not every first lady who followed would be counted as an activist but they all kept the office, the staff, and the platform she bequeathed them.

“She reminded me to make the role of first lady my own, just like she did,” Michelle Obama said in a statement on Sunday, recalling their lunches together during her own White House years. “I’ll always remain grateful for her support and her generosity.”

Dr. Biden travelled with her husband to visit Mrs. Carter and her husband just a few months after moving into the White House in 2021. Like Mrs. Carter, Dr. Biden campaigned for her husband in places he could not go. Dr. Biden, who teaches at a community college in Northern Virginia outside Washington, is the first presidential spouse to hold an outside job.

“There really is no comparison between first ladies,” he said. “They’re all unique and recreate the job in their own style. But her love and admiration for Rosalynn Carter was personal and boundless.“