JOHANNESBURG » It was the 20th anniversary of Nelson Mandela's release from prison, a high point in South Africa's history, but for the current president, Jacob Zuma, who delivered his state of the nation address on Thursday, the moment arrived at a low point in his own 10-month-old tenure.

As the frail Mandela, 91, basked in an affectionate welcome from Parliament, the contrast between the exalted promise of South Africa's transition from apartheid to multiracial democracy and its messy, if vibrant, political present never seemed sharper.

Zuma's presidency has been shaken by his admission that despite his exhortations for South Africans to prevent the spread of HIV by using condoms, he had unprotected sex with yet another 30-something daughter of a family friend, fathering a child out of wedlock.

Zuma, 67, who has 20 children, 3 wives and a fiance, apologized for the affair last weekend, several days after the story broke, and sought to reclaim the moral high ground on Thursday in a live televised speech before Parliament. He made no mention of the scandal, which has transfixed the nation and emboldened his critics, but repeatedly paid tribute to the man considered the father of the nation.

“;President Mandela united this country behind the goal of a nonsexist, nonracial, democratic and prosperous South Africa,”; Zuma said.

After a day of pageantry to commemorate Mandela's walk to freedom, Zuma strolled across a red carpet into the Parliament building in Cape Town to deliver his address.

He campaigned on a platform of more jobs and improved education, but both goals have suffered setbacks. Official statistics released this week showed that the country, hard hit by the global economic crisis, lost 870,000 jobs last year, leaving over a third of the labor force unemployed or too discouraged to look for work. And results of the examinations of high school seniors showed last month that performance had declined for a sixth consecutive year.

In his speech, Zuma announced that the government would begin providing teachers with detailed daily lesson plans and regularly test the literacy and numerical competence of elementary school students, sharing the results with parents. He also proposed measures to get South Africa back to work, including subsidizing the costs of hiring inexperienced young workers.

“;The most urgent focus of policy change must be interventions to create jobs for young people,”; Zuma said.

The charismatic son of a maid and a man who spent a decade imprisoned with Mandela on Robben Island, Zuma has a more down-to-earth, populist style than his aloof, prideful rival, Thabo Mbeki, who was deposed from the presidency in 2008 by his own party, the African National Congress, after nine years.

Zuma got the chance to begin his stint as leader with a clean slate when prosecutors dropped corruption charges against him just weeks before the April 22 elections, arguing that the legal process had been unfairly manipulated.

Early on, even Zuma's skeptics praised his Cabinet appointments and pragmatic focus on the country's fundamental problems: a failing education system, one of the world's worst AIDS epidemics and high rates of joblessness and violent crime.

His new education minister, Angie Motshekga, frankly acknowledged the government's failure to hold principals and teachers accountable for effectively educating children. Zuma also broke with Mbeki's discredited views on AIDS and strongly backed his new health minister, Aaron Motsoaledi, in devising a better strategy to combat the intertwined AIDS and tuberculosis epidemics.

But there has recently been unease about whether the country has begun to drift under Zuma, and even some of those rooting for his success are waiting for proof that his government has the managerial and political moxie to deliver on his promises.

“;There's a lot of rhetoric that does indicate change, but it hasn't hit the ground yet,”; said Graeme Bloch, a researcher at the Development Bank of Southern Africa, referring to education in particular.

That assessment could apply just as well to other realms. Zuma, whom supporters depict as a unifying figure, has not put a halt to the venomous squabbles within the governing alliance over nationalizing mining and leadership of the state-controlled power utility. But Zuma could also be letting the feuds play themselves out without seeming too heavy-handed.

Business people initially worried that Zuma's leftist allies would push him to adopt more populist economic policies, but that does not seem to have happened. After his speech on Thursday, Cosatu, the trade union federation, issued a statement saying that it was “;somewhat disappointed,”; mentioning that he said nothing about curtailing practices unions see as exploitative.

Politically, news of Zuma's affair has proved a blow. His party initially insisted that “;there is nothing wrong that the president has done.”; But after the public uproar failed to die, he apologized.

In a separate case, Zuma admitted in 2006 to having unprotected sex with an HIV-positive 31-year-old woman who was the daughter of a close comrade from the struggle. The episode surfaced because she accused him of rape. He was tried and acquitted.

Now the pattern has repeated itself. Members of Parliament gasped Thursday when Zuma praised his new child's mother's father, Irvin Khoza, who leads the nation's World Cup organizing committee. The fact that Zuma had again had sex without a condom with a much younger woman has renewed questions about his judgment in a country where AIDS has reduced life expectancy.

“;He just illustrates that problem,”; said Salim S. Abdool Karim, who runs the Durban-based Center for the AIDS Program of Research in South Africa. “;We have to convince him and everyone else to change our sexual norms.”;

Zuma is an extraordinarily resilient politician, but analysts say the latest scandal may weaken his political authority, even if it does not cost him a second term. William Gumede, the author of a book about South African politics, said the risk was always that Zuma's “;shambolic”; private life and personal finances would come to dominate public life and paralyze the government.

“;This moment has arrived,”; Gumede wrote this week in the newspaper The Sowetan. “;The floodgates have been opened. It will be difficult to close them now.”;