National Agenda : Mandela After One Year: Public Acclaim, Private Pain : The president’s stature has grown as he helps unite South Africa. But his personal life is troubled.

Nearly 77 years old and clearly slowing down after a grueling first year as president, Nelson Mandela was ready when a reporter gingerly asked about his health.

“I would like to challenge Mike Tyson. That is how I feel!” Mandela, who was an amateur boxer as a young man, quipped with a grin.

But, he conceded, “At this age, one has a lot of ailments.”

Mandela has had cataract surgery, wears a hearing aid and walks stiffly because of poor circulation in his feet. Like many older men, he’s been treated for a prostate problem. He grabs a nap most afternoons.

But when democratic South Africa celebrated its first birthday April 27, its charismatic president seemed to have few other troubles.

He is not so much respected here as beloved. Although he was already a mythic figure for enduring 27 years in prison in the fight against apartheid--South Africa’s former legal separation of the races--his stature and moral authority have grown as he has helped to unite the bitterly divided nation as its president. Abroad, he is hailed as a beacon of hope in an era of gloom.

But if Mandela’s health is good and his place in history secure, his private life is neither. A stable home life may be the one achievement that has eluded this remarkable man.

“I think that he’s very lonely,” said Archbishop Desmond Tutu, a longtime friend and fellow Nobel peace laureate who speaks with Mandela regularly.

Tutu said the president has phoned repeatedly to share his pain over his 1992 separation from his wife, Winnie, after 34 years of marriage. In a recent call, Tutu said, Mandela confided his anguish over being forced to fire her twice from a Cabinet position, apparently for insubordination.

“I know he’s loved Winnie very much,” Tutu said, picking his words carefully. “And you know, it’s a huge hole in his life.

“Maybe sometimes we forget too easily the cost of our freedom,” Tutu added after a pause. “And the cost to him is being alone. He comes home from the office, and it’s a big house and he’s alone. That is probably pain that has grown in the past year. He has not stopped making sacrifices even now.”

Mandela’s overwhelming celebrity--polls show astonishing 90% approval ratings--may be his greatest problem. He has become indispensable to the nation.

He is constantly called upon to solve mundane problems, from mediating a supermarket strike to calming disgruntled soldiers. And he still tries to spend each Monday at Shell House, the drab Johannesburg headquarters of the ruling African National Congress (ANC), to supervise routine party business.

Such duties keep him from adventures abroad. Mandela has refused pleas by foreign leaders to use his credibility and charm to mediate in the Middle East, Rwanda, Angola and elsewhere. He also declined President Clinton’s personal request last year to send peacekeeping troops to Haiti.

“He’s been raised to demigod status,” complained Eugene Nyati, a black political analyst and private business consultant who heads the Center for African Studies in Johannesburg. “South Africa depends too much on the persona of Nelson Mandela. He needs to rely less on his stature and more on his subordinates and systems.”

The workload has taken its toll. His doctors and aides complain that Mandela pushes himself with 17-hour workdays that start before dawn. He has repeatedly appeared exhausted in public and has canceled engagements and otherwise trimmed his schedule to allow for rest.

Mandela doesn’t hang around his four homes (two official, two private) and wait for the phone to ring.

He is close to Graca Machel, the widow of Mozambique’s first president, Samora M. Machel. Mandela’s staff denies a romance. But the president quietly flew to Maputo, Mozambique’s capital, one recent weekend, and a Western diplomat swears the pair were seen walking hand in hand.

Two of Mandela’s daughters, who grew up without him, recently went public to deny reports that they had “abandoned” their father for their mother in their parents’ bitter dispute.

Although they were noticeably absent from Mandela’s side during a visit by Britain’s Queen Elizabeth II in March, both women insisted that they have not broken with their father, nor he with them.

“It looks like a nightmare, but it is not,” Zenani Dlamini told the Sunday Times of Johannesburg. Dlamini, 37, accompanied her father at his inauguration in Pretoria last May.

Mandela marvels at his sudden popularity among the white Afrikaners who once demonized and imprisoned him. During a 90-minute breakfast with foreign correspondents just before the celebration of his first year in office, he recalled visiting a Dutch Reformed church, once a key pillar of apartheid, a month after his inauguration.

“If I had been to that service two years before, the security police would have had to defend me from people who wanted to kill me out of hatred,” he said. “This time, they had to defend me from people who wanted to smother me with love.”

And he agrees to unusual stunts. Before the anniversary, a load of “Mandela-bilia”--including running shoes and reading glasses that he wore in prison--was auctioned off in Cape Town. The money will be used to help pay overdue phone bills run up by the local unit of the ANC, his political party, during last year’s elections.

The gray suit and black Bally loafers that Mandela wore when he finally walked out of prison a free man in February, 1990, will be auctioned in New York or Washington this month, organizers said. The money will go for training of ANC staff.

These days, Mandela is usually relaxed in dress, given to wearing brightly colored, waist-length, open-collar shirts rather than suits and ties. He is warm and witty in public, an imposing figure of serene dignity.

Yet in private, he can be cold and imperious. Ask former President Frederik W. de Klerk, who freed Mandela from prison, shared a Nobel Peace Prize with him in 1993 and now serves as his deputy president in a five-year coalition government.

Over dinner one night last month, De Klerk noted bitterly that he has never dined alone with Mandela. Despite their long ties, he added, neither has ever called the other by his first name. He formally addresses Mandela as “Mr. President” and is “Mr. Deputy President” in return.

Thabo Mbeki, the other deputy president and Mandela’s likely successor, is closer to him. Mbeki writes most of Mandela’s major speeches and has functioned as the president’s chief emissary and trouble-shooter with Winnie Mandela, among other difficult figures.

Critics say Mandela is too indecisive, too loyal to his friends and too lenient on lawbreakers. And Tutu criticizes Mandela for lending his name and prestige to the country’s arms-export industry.

“I told him this is one area where one day he’s going to find himself picketed by the people who used to support him,” the archbishop said.

To keep fit, Mandela enjoys a brisk walk at sunrise each day with his bodyguards. The health kick isn’t new: Mandela had a strict exercise regimen during his long years in prison.

“On Mondays to Thursdays, I would run on the spot in my cell in the morning for up to 45 minutes,” he wrote in his autobiography, “Long Walk to Freedom.” “I would also perform 100 fingertip pushups, 200 sit-ups, 50 deep knee-bends and various other calisthenics.”

The best-selling book has been short-listed for literary prizes in Britain. Mandela isn’t impressed.

“One of the things puzzling to me is that so many people around the world are so interested in cheap literature,” he deadpanned at the reporters’ breakfast. “If I were you, I wouldn’t read that book.”

As for his plans, Mandela said he looks forward to retiring when his term expires in 1999. His chief goal, he said, is to spend time with his 21 grandchildren. Unlike the aides and flatterers around him, he said jokingly, “It’s easy for them to say, ‘Grandfather, you are foolish.’ ”