For a while he seemed to be Barack Obama in reverse. Whereas the American president was elected with such stratospheric expectations that the only way was down, South Africa's Jacob Zuma came to power in a fog of anxiety and misgivings, ensuring that an early lack of gaffes or scandals would give his sceptics a pleasant surprise.

He made the right noises about dealing with township poverty and the political crisis in Zimbabwe. He gave a speech on Aids that was hailed by campaigners for burying the ghost of former president Thabo Mbeki's flirtation with denialism. Even Helen Zille, the feisty leader of the opposition, had to admit that Zuma has charm.

So when he married his third wife in January, barely an eyebrow was raised. South Africa seemed at ease with its polygamous Zulu president. But a storm was brewing. A few weeks later, the thunder came.

A Sunday newspaper revealed that Zuma had fathered a child in an adulterous relationship with the daughter of a family friend. Zille and other opposition politicians were quick to seize on the discrepancy between Zuma's Aids rhetoric and his unsafe sex practices.

This was his 20th child, as far as is known. One columnist noted: "President Jacob Zuma risks being remembered as Father of the Nation, but for all the wrong reasons."

The debacle was compounded when, like many politicians before him, Zuma misjudged the national mood by condemning journalists for probing his private life and "questioning the right of the child to exist". As criticism swelled and the lack of support from his party became telling, he was forced to back down and eventually issue a full apology for the damage done.

Then came Zuma's state of the nation address to the South African parliament, rescheduled for prime time television on the 20th anniversary of Nelson Mandela's release from prison. It is not the first time that Zuma has sought to bask in the glow of the national saint.

Mandela himself was in the parliament building in Cape Town to hear the speech, which is a bit like trying to dazzle while George Washington is sitting in the front row. Unfortunately, Zuma was now the one who had set expectations impossibly high. His speech, in the view of most critics, was a lacklustre dud, as he stumbled over words and failed to provide either soaring poetry or meat in the sandwich.

The veteran journalist and political analyst Allister Sparks said: "The combination of 'Babygate' and that hugely uninspiring speech has left our president looking like a pricked balloon – and the nation feeling deflated with him."

Zuma's party, the African National Congress, unites admirably at election time but currently resembles a fragile and fractious alliance. The left is at odds with the right; the trade unions and communists are clashing with the party's outspoken youth league. There are calls for a strong leader to impose discipline.

But Zuma, says Sparks, is already "a lame-duck president in the first year of his first term. Will there be a second term, or will Zuma be dumped in 2012? At this point the only certainty is continued uncertainty."

Another commentator, Richard Calland, wrote in the Mail & Guardian newspaper: "Faced with a lame duck president, some are already reaching the conclusion: Zuma should go – and go now."

So far, so familiar to any student of the warp and woof of western politics. But every country has its own etiquette. Before his speech, Zuma was led into parliament by an imbongi – a traditional poet – singing his praises with gusto from beneath a crown of porcupine quills. ­Winnie Madikizela-Mandela, according to one newspaper report, caused a major logistical headache by taking a seat reserved for Zuma's first wife.

Then, with parliament last week responding to Zuma's address, the opposition MP Mluleki George, of the Cope party, said: "It appears that the nation is being deliberately led to lawlessness, with absolutely no morals and respect for its people."

The deputy speaker of the national assembly ordered him to withdraw the remark on the basis that it "creates the impression that the president or his government is inciting lawlessness". He refused and opposition MPs from both Cope and the Democratic Alliance staged a walkout in protest.

Among them was Dianne Kohler Barnard, so frustrated by events that she uttered the word "fuck". This is not the done thing in the house and she was suspended by her party for five days.

Another case of bad manners then transpired, with much harsher consequences. Chumani Maxwele, a 25-year-old sociology student at Cape Town University, was out jogging when he waved away, or showed a middle finger to, a blue-light convoy carrying the president.

Maxwele was allegedly bundled into a police vehicle at gunpoint, had a bag pulled over his head and was intimidated, threatened and taken to court on charges of crimen injuria – the common-law South African crime of "injuring dignity" – and resisting arrest.

Helen Zille, of the Democratic Alliance, said the police actions were "reminiscent of Robert Mugabe's Zimbabwe, which the African National Congress is increasingly trying to emulate". It was noted that five years ago Mugabe amended Zimbabwe's traffic legislation to make it a crime to swear or gesture rudely at his motorcade.

Zuma has more challenges to come. Last week I was at the University of the Witwatersrand in Johannesburg for lectures by Madikizela-Mandela and Julius Malema, the president of the ANC youth league. Malema's rhetorical flourishes were greeted with cheers, applause, horns, dancing and revolutionary songs, which all felt like more fun than I remember in my university days.

He told the energetic young students: "The struggle is not over. The struggle is starting now. The struggle of fighting for the economic emancipation of our people. The struggle to decolonise the economy of South Africa. The struggle to take the commanding heights of the economy in the hands of white males into the hands of the people of South Africa."

Malema has a gift for oratory and for tapping into populist sentiment with a direct and powerful message. President Zuma is currently in drastic need of the same.