Nelson Mandela's appearance at an African National Congress rally in the Eastern Cape yesterday is a timely boost for the ANC leader, Jacob Zuma, in the run-up to April's general elections in South Africa. But the endorsement of the universally revered former president comes as a rare ray of light amidst the gloom enveloping Mr Zuma and his party.

The ANC leader might have been cleared of rape charges in 2006, but serious corruption charges relating to a 1998 arms deal still hang over him. Even if Mr Zuma is elected president in April, he will be expected to appear in court in August on charges of corruption, money-laundering, racketeering and tax evasion.

There is continued discord within the ANC too. The party's spokesman, Carl Niehaus, was forced to resign last week after admitting fraud. And the infighting continues between Zuma supporters and loyalist backers of Thabo Mbeki, who was ousted as president last year.

Another headache for Mr Zuma is the formation of a new Congress of the People (Cope) party, made up of ANC defectors. Cope will not win in April's election, but it might deprive the ANC of its two-thirds majority in parliament, allowing it to block changes to the constitution. Another challenger to the ANC, the Democratic Alliance, led by the tenacious mayor of Cape Town, Helen Zille, is also expected make progress in April.

For the first time since the end of Apartheid in 1994, the ANC has some serious competition at the ballot box. The political landscape after this poll is likely to be considerably more diverse than South Africans have been used to in the years since the crumbling of the Apartheid regime. And a damaging constitutional crisis could be looming if Mr Zuma's corruption trial goes ahead. But, in the immediate term, challenges to the ANC hegemony in these elections are to be welcomed.

South Africa's glaring social problems – widespread poverty, rising violent crime and an Aids epidemic – are more likely to be effectively tackled in a competitive democracy than a one-party state. However messy the process, the transformation of South African politics is necessary.