Leading article: Zimbabwe's war of succession

Rumours of the ill-health of Robert Mugabe are greatly exaggerated, the man himself insisted yesterday in a rare interview evidently given to allay suggestions that he is about to die. Recent pictures of Mr Mugabe showed him walking unsteadily and needing help to negotiate stairs. So up popped the Zimbabwean president to insist he was "fit as a fiddle". Whether he is or not, there is little doubt that Zimbabwe could be thrown into serious turmoil if Mr Mugabe dies in office. The man who has ruled the country for the past 30 years has indicated that he may run for office again in 2012, or whenever. And there is no unambiguous provision under the current constitution for what happens if the president dies in office.

The battle for succession within his Zanu-PF party is hotting up. Given the ruthlessness displayed by competing factions in the past, the process could become a violent one. In some ways change would mean no change. The two chief competitors for the throne are the defence minister, Emmerson Mnangagwa, and the most senior survivor from the liberation war, general Solomon Mujuru, whose wife is the country's vice-president. Both are implicated in Mugabe cronyism; both were named in a report this week on profiteering in blood diamonds. Zanu-PF may collapse when Mr Mugabe dies. But bitter infighting could ensue, which will result in one party conceding or one declaring the constitution suspended and placing Zimbabwe under military rule. The generals, all Mugabe creatures, are a potent force.

So what of Morgan Tsvangirai, who won the last election but who was brushed aside by Mugabe with the rest of the world doing little in response but bluster? His so-called power-sharing government with Mugabe has stabilised the economy (though the vast majority of people continue to live in extreme poverty) but Mugabe retained control of all the key ministries, the military, the police, the intelligence services and the judiciary. He has even refused Mr Tsvangirai access to the prime minister's official residence. Unless Mr Tsvangirai's Movement for Democratic Change is ready to embark on mass uprisings on a level from which it flinched last time, whoever takes control of Zanu-PF will, as the MDC minister of finance, Tendai Biti, put it bluntly, "continue to urinate on us".

Only one man can change that. Jacob Zuma, the president of South Africa, must keep up the pressure for a new constitution for Zimbabwe – in which the outcome of elections must be respected and not set aside by a ruling clique. Without that, the manoeuvrings over the succession to Robert Mugabe will be meaningless.