President Jimmy Carter and his wife Rosalynn celebrates 65 years together

ATLANTA President Jimmy Carter and his wife Rosalynn endured the grind of political campaigns and the pressure cooker of the White House. But their marriage faced its stiffest test in the years after his presidency ended.For the couple, who celebrate their 65th anniversary Thursday, it came when they decided to write a book together in the mid-1980s. Soon, they were sending each other nasty notes and squabbling about minor differences. They were ready to hand back their book advance when an editor arranged a ceasefire: Each would write their own sections, and sign them with their initial.

"They're not all disagreements. There are some things I knew and that you knew we wanted to put in," Rosalynn says now of writing the 1987 book, "Everything to Gain: Making the Most of the Rest of Your Life."Jimmy cuts in. "Well, I would say they were disagreements," he said, adding with a chuckle: "I was amazed at how paltry Rosa's memory was."

There are bound to be some tense moments in the second-longest marriage in the history of the American presidency. In the long line of American presidents and first ladies, only George H.W. and Barbara Bush have been married longer.The Carters have known each other for more than 80 years, dating back to when the president was 4 years old and he lived down the street from Rosalynn, who was just an infant. Rosalynn was best friends with Jimmy's little sister, but the two didn't start dating until Jimmy returned to southwest Georgia in 1945 while on leave from the U.S. Naval Academy.

As he tells it, he was seeing a local beauty queen at the time but he agreed to a date with Rosalynn because he wanted an excuse to go see a movie. By the time it was over, he was smitten."The next morning I told my mother she's the one I want to marry," he said. "It was just an overnight infatuation, a love affair with me."

Rosalynn wasn't so sure. She rejected his first marriage proposal - "I was very young," she explained - before acceding a few months later.These days, Carter likes to say Rosalynn is his most trusted adviser and his equal partner. He brings her along on trips around the world brokering peace deals and fighting diseases, and he makes sure to arrange plenty of time for the media to hear about her latest project. But it wasn't always so.

When Jimmy resigned from the Navy and returned to their hometown of Plains, Ga., to take over his ailing father's peanut business, he said it was a snap decision. And he only told Rosalynn he was running for the Georgia Senate as he was changing into a suit before driving to town to qualify as a candidate.

"That's a strange thing and now a great mystery to me," he said. "The first few years I made the basic decisions, and I would just inform Rosalynn what I had decided."

She cuts in: "Total housewife."

"Now it's inconceivable to me because I don't make any decisions now without asking Rosalynn first, and generally I just do what she suggests," he said. "We have a full and equal partnership, and have had since I first got involved in politics."

Rosalynn said she was OK at first that he didn't consult her, although she admitted to pouting for about a year when they moved back to Plains after living in places like Hawaii and New York. Things started to change, though, as Jimmy got more involved in politics and Rosalynn started making the tough calls in the family business.

"We just developed a relationship that was more equal," she said.

"I'd say we learned to cooperate on things but to give each other plenty of space," he said.

In the White House, he'd often listen to her counsel, but sometimes wouldn't heed it. Jimmy had a knack for tackling politically unpopular decisions, such as handing over the Panama Canal, that Rosalynn and his advisers wanted to put off.

"I would say `Why are you doing this now, why don't you wait for the second term?'" she recalled. "And he would say, `Suppose I don't have a second term.'"

"Who was right?" he joked. He added, though, he doesn't regret not heeding her advice in that fight.

"It would have just been out of my character," he said. "If I had it over to do over again, there's no doubt I would have done the same thing."

The Carters say their keys to a long, fulfilling marriage are fairly simple. They're loyal to each other. They communicate. They try not to go to bed fighting. They exercise together and both took up fly-fishing, downhill skiing and cycling so they could spend more time with each other.

And they've resolved never to write another book together.

"The bottom line is we've been able to resolve our differences," said the former president. "And I'm her trusted editor and she's my best editor. But I know that the final words are mine."

"And I know that my final words are mine," Rosalynn interjected.

Like any good marriage.