A huge picture of Nelson Mandela hangs along the concrete side of Luthulu House, the African National Congress headquarters in downtown Johannesburg.

It bears a message from the summer, wishing Mandela a happy birthday, and towers above city streets much as the man himself still seems to hover above this country like a talisman.

It needs one. Eighteen years after the end of apartheid, the gap between South Africa’s rich and poor is among the widest in the world. White South African households still take home six times more than black households.

What's more, the modern-day leadership of the freedom movement that Mandela led from behind bars — eventually to an extraordinary period of reconciliation and hope — now stands accused of tarnishing his legacy, the result of a host of corruption allegations leveled against those at the top.

Last week, driving the point home, a group of senior clerics wrote to the South African president and current ANC leader, Jacob Zuma, accusing a "generation of leaders" of having lost their "moral compass."

"When the ANC took power in 1994 I think in my mind I felt like we made it," says Carol Dyantyi, who runs a non-profit AIDS mission in Soweto, caring for children who lost their parents to the disease. The mission is not far from Vilakazi St., where Mandela and his fellow Nobel Peace Prize laureate, Archbishop Desmond Tutu, once lived.

"When I look at the ANC now, I am just saying, 'Lord what happened?'" Dyantyi says. "How did they get their priorities wrong? How could a movement not be able to differentiate between right and wrong when it cost so much bloodshed?"

The public protector

Thuli Madonsela is South Africa's recently appointed anti-corruption tsar, with the official title "Public Protector."

An elegant, courteous woman, she travels the country from her base in Pretoria investigating charges ranging from police corruption to the failure of local governments to provide proper facilities and schools.

"We haven't lost our way yet," she says, "but we are on the way to losing our way if we don't correct injustices within our administration and challenges such as corruption.

"And corruption is endemic, there are no two ways about it."

South Africa, in fact, has fallen several points, to 69th place, on Transparency International's list of the world's most corrupt jurisdictions. That's tied with Brazil. But it is also behind even such troubled African countries as Ghana, Lesotho and Rwanda.

For her part, Madonsela has solid ANC credentials. She helped draft the country’s constitution and has become something of a folk hero for her work as public protector. But she admits she has her detractors and they have been making her campaign difficult.

"There has been subtle pressure in the form of creating stories that try to discredit the office," she says. "There are people that are going to each and every complainant that has dealt with my office to try and get those complainants to complain and say they were not treated properly.

"What we think is happening is an attempt to set my house on fire."

Supporters of former ANC youth leader Julius Malema challenge his ouster from the ruling party for what they feel are trumped up charges. (Reuters)

Madonsela has taken on the likes of former ANC youth leader Julius Malema, a political firebrand accused of influencing tenders in exchange for kickbacks in his home province.

She is also investigating the latest scandal to attach itself to Zuma himself. The president is accused of spending some nearly $28 million in taxpayer money to upgrade his ancestral home near the village of Nkandla in KwaZuluNatal.

In the South African press, it is being dubbed Nkandla-gate.

Zuma 'exposed'?

The Zuma estate sits on a gentle slope in one of KwaZulu-Natal’s rolling valleys. It's a collection of buildings with traditional thatched rooftops and is surrounded by a security fence. From a distance, it looks like an African version of TV's Southfork.

The scale of the place doesn't really become apparent until you see the aerial photo, which the local papers have been happy to publish.

The complex is also said to have a heli-pad and underground bunkers. But the locals don't seem to have any problem with the extravagance, they feel they have benefited from living near the president.

"What makes it good is we get so many opportunities to do things we couldn't do before," Sihlenzous Nzuza, a student, told me last week. "Sometimes Mr. Zuma gives us free gifts and food during December."

Elsewhere in the country, there has been a different reaction. Adriaan Basson, the author of a new book, Zuma Exposed, says "there has been a huge outcry in South Africa over this kind of expenditure. It was seen as an obscene amount of money to be spent on one person.”

Madonsela, the public protector, is careful to point out that nothing has been proven against Jacob Zuma as yet.

"On the question of the president I would like to indicate that he has yet to be tried on the allegations of corruption. On the issue that I’m dealing with on the upgrading of his home in Nkandla, I haven’t made my findings yet."

Still, as more than 4,000 ANC delegates gather in Mangaung this week for party conference that is held every five years, there is a deepening impression of a movement and a country in crisis.

Zuma's $28-million compound in his home village of Nkandla, the latest in a series of controversial incidents that has dogged his presidency. (Associated Press)

Zuma, in fact, is now facing an unusual, last-minute leadership challenge from his own deputy president, Kgalema Motlanthe, a testament to just how volatile leadership politics here have become in recent weeks.

"I think the person of President Jacob Zuma and the scandals that have surrounded him for a long time first led to a splinter in the ANC in 2009 and I believe it will continue to drive people from the ANC towards some or other form of the opposition," says South African political commentator Justice Malala.

"I think our society is largely trying to find itself and the choices we make will determine whether we go a very unfortunate route, that has been travelled by many, many other African governments and many other post-liberation governments, or we reclaim the high road that is exemplified by people like Archbishop Tutu and we become a better democracy."