Rosalynn Carter had some rough moments watching Jimmy Carter go down in defeat to Ronald Reagan, once on Election Day when she slipped into their White House bedroom and cried a little bit and another time a few days later when Israeli Prime Minister Menachem Begin paid a visit.

She was sorting through her briefcase to reread some of her old campaign speeches when she heard trumpets on the front lawn. Looking out the window of her White House living quarters, she saw Begin and suddenly, as she told it later, she broke down and cried.

In her first interview since the campaign ended, the first lady spoke with seven reporters at the White House yesterday about the frustrations and the joys of living with the president. She said she believes that the American people eventually will realize that Jimmy Carter was "a very successful and a great president" and that history will bear her witness.

"I don't feel bitter towards the American people," she said in a wide-ranging give-and-take lasting nearly an hour. "I don't see it at all as a rejection of Jimmy Carter. I see it as a protest vote, and I can understand their feelings."

Seated in the family's quarters upstairs, the woman once dubbed "The Steel Magnolia" discussed not only what she thought went wrong -- "The problems are difficult, and it's difficult to explain to people why things happen" -- but how they both came to grips with the realization that he was not going to win.

She said she never thought he would lose until two days before the election.

She was at the White House and he was in Chicago when he called her at 5 a.m. to tell her about the Iranian demands for the return of the hostages.

"He said, 'I'm going to have to tell you this -- I don't know what's going to happen. This could cause the election to go either way, and we have to accept that. But we have to react to that, and I have to come home.' He said, 'I want you to know that and to know that I love you.'"

She flew off to campaign, adding to her own schedule some of Carter's schedule. In Wisconsin, on Monday morning, television was saying he didn't have a chance to win. In Huntington, Ala., after a long day of campaigning, her plane was about to leave when she decided to get off and call Carter pollster Pat Caddell. He told her it didn't look good but to call him again around 1 a.m.

"I figured then we probably had lost," Rosalynn Carter said.

She went to bed in Plains that night, and the next day the president arrived with the news that he was down in the polls.

"Does that mean we've lost?" she remembered asking him, "and he said, 'Yes.'"

The first lady spoke out on other subjects:

Dismantling of the Carter programs -- "I read it with the most detached feeling I have ever had, I read all the things they're going to do. Even on Election Night it was like it was not me.It's frustrating, but the thing about it is, what else can you do?"

Running for public office -- "Not now."

Speaking out -- "I worked very hard to stay here, but I didn't get to, so I'll continue to speak out about things like ERA that are important to me. I don't intend to go to Plains and just sit down and be lost."

Family life in the White House -- "I've been proud of the way my children reacted to the pressures."

Sense of relief it's over -- "Sometimes when I read about some of the problems and what they plan to do, I have a feeling that you hope it works because you really care and are concerned for the country."

Moral Majority -- "It bothers me when you try to define a Christian as one who stands for certain legislation . . . they believe if you're for the Department of Education, you're not a Christian. Those things frighten me and I think that had a great impact on people, just hearing it continuously."

The first lady described how she and the president returned to the White House from Plains on Election Day to find their son, Chip, and several others, waiting for them. "The girlfriend with Chip had tears in her eyes, and then I went to the bedroom and cried for a little bit," she said.

Later, she said, when she and the president were taking a nap, they were awakened by Amy, who said she was "depressed about this election. Jimmy told her we did the best we could and we were just going to lose. So she said, 'Do I have to go to violin?' And I said no, so she stayed home."

The next afternoon, Amy went to school, where, earlier, her father had won in a student election with 80 percent of the vote. "I had to be tough," Amy told her parents. "All my friends were crying. I was the only one who wasn't.

Asked how she felt about criticism that she had been too dominant as first lady, Rosalynn Carter said it was important to put it in perspective.

"I don't think I'm very different from people in the country today. Women work, but they also have a strong family life. I combined work and family life and outdoor life and companionship with my husband -- who likes to jog and fish -- with being a mother.

"I've enjoyed being a hostess," she continued. "I've developed international interests, and I have a varied life and enjoyed it. I think that is not different from just ordinary people. Some women would rather stay at home and be a mother. Some work because they have to, some work to be fulfilled."

She claimed it doesn't bother her that critics call the Carter White House inelegant." "I've heard that ever since we've been here, and I know what we did. We had the greatest artists and a range of culture and art. And one thing I'm really proud of are the White House art acquisitions."

She said under her husband, the White House was an "open, friendly, warm" place where there were more "ordinary people" invited than ever before.

She thinks Jimmy Carter is a great president because "he redefined the Democratic philosophy and to some extent, maybe, some Democrats were not ready for that." She said her husband was "practical, fiscally responsible and compassionate, and that's what the Democratic Party is going to have to be."

The Carters will return to live in Plains, but she said they expect to spend considerable time in Atlanta, one of several possible locations being mentioned for the presidential library.

Asked if she planned to run for public office, she said "not now," but she did not rule it out in the future. "I don't know what will develop," she said, laughing.

She probably will write a book drawn from her diary, which she said she did not keep too faithfully her first year at the White House.

While she spoke, Amy returned from sshool and, with her cat, crawled behind a chair to listen. A little later her mother invited everybody in to see Amy's bedroom with its four-poster bed and view up 16th Street.

The first lady said that there had been some bad moments these past years, but that the worst were when her son, Chip, and his wife, Caron, separated, and when the attempt to rescue the hostages failed.

She said she will show Nancy Reagan through the White House and introduce her to chief usher Rex Scouten later this week. As for advice, she will tell Nancy Reagan that a first lady can make the job anything she wishes.

After conducting a quick tour of the family dining room, kitchen and the Queen's Bedroom, she pulled on her coat. She followed Amy, carrying her violin, into the elevator and headed off to oversee Amy's lesson. A little later, she telephones her press secretary, Mary Finch Hoyt, concerned that she had not made it clear to reporters that she had experienced some "weak moments" in Jimmy Carter's defeat. She wanted them to know that one of them had been when she broke down the day Begin arrived at the White House.

Yesterday she talked excitedly about their new life ahead.

"I don't think it's going to be quiet," she said. "You go through one phase of your life and then you go on to the next phase.

"I think the '80s will be very exciting," she said. Catching herself, she giggled, "Well, I thought the '80s were going to be exciting." She paused. "I guess they will be."