Shifts in African National Congress (ANC) membership within South Africa's provinces have given President Jacob Zuma a fighting chance of holding on to the party leadership and the presidency.

The number of ANC members in the southeastern province of KwaZulu-Natal might seem like a detail only of interest to South African political scientists.

In fact, the number may well be decisive in helping Zuma remain in charge of Africa's most powerful nation and her largest economy.

This December 4 500 ANC delegates will gather to elect a party leader for the next five years.

He or she will almost certainly become the next president of the country, thanks to the party's electoral predominance.

Five years after ousting president Thabo Mbeki in an act of political regicide at the last ANC electoral conference, Zuma could face the same fate in December.

Deputy President Kgalema Motlanthe is widely tipped as one possible challenger. He could announce his candidacy as soon as this week.

According to a recent TNS poll Motlanthe has a 51% approval rating to Zuma's 48%.

But as the race gets underway, the ANC announced Wednesday that a surprising 36% rise in membership in KwaZulu-Natal means at least 974 of the 4 500 conference delegates will come from Zuma's home province.

It is by far the biggest representation of any province.

For an incumbent whose administration has been marred by rolling strikes, high unemployment and social unrest, that is nothing short of a godsend.

In the race for 2 250-plus ANC delegates, every vote will count, according to Mari Harris, managing executive at local pollsters Ipsos Markinor.

A complex mix of loyalty, personal advancement and ideology, as well as regional and tribal politics, will all play a role in corralling delegates.

Harris predicts that the largely rural Eastern Cape, home to Nelson Mandela and long the heartland of the ANC, will back Motlanthe.

Although the dominant tribe in the Eastern Cape is Xhosa, members are more likely to go for Tswana-speaking Motlanthe, than Zuma, who is a Zulu.

"The Xhosa don't have a candidate," said Harris.

She also predicts that Gauteng – which includes Johannesburg and the capital Pretoria – will favour Motlanthe.

Indeed, ANC rising star, Gauteng province chairperson and culture minister Paul Mashatile has already said the "ANC must change this year," while calling for a "renewal of leadership."

Together, Gauteng and the Eastern Cape account for 1 176 delegates. By striking the right pacts Motlanthe could significantly increase that total.

His recent courting of ousted party firebrand Julius Malema appeared to have paid off Wednesday when the ANC's Youth League, which still backs Malema, called for a "radical and urgent change" within the party and backed Motlanthe as leader.

With only 45 delegates, the Youth League is unlikely to tip the balance of the leadership contest – but it could prove a thorn in Zuma's side.

Malema could help deliver some or all of the 574 delegates in his home province of Limpopo.

It is against this backdrop then that KwaZulu-Natal's increase from 608 votes in 2007 to 974 today may prove crucial for Zuma.

"At this stage I think he will still carry the vote, with a small majority," said Harris. "But everything can change."