When researching his official biography of Nelson Mandela, the late Anthony Sampson arrived late for lunch at my house in Cape Town in a filthy temper. "If Thabo Mbeki is going to be president," he fumed, "he'll have to get over his bloody insecurity!"

That was exactly a decade ago; Mbeki was Mandela's deputy president and Sampson never did explain what had made him so irate. But we now know the answer to his longer-term concern: Mbeki, it seems, didn't get over that insecurity.

One result is his own crushing defeat last month for the job of heading the African National Congress (ANC). The fact that Jacob Zuma had a clear run was entirely Mbeki's fault. As president, Mbeki ruthlessly sliced his most obvious successors out of contention. Then, by insisting on standing for a third term as ANC president, he blocked more popular candidates from opposing Zuma.

It is the consequence of an all too common flaw in authoritarian leaders: a mix of insecurity and arrogance. Spectacularly the author of his own misfortune, this has rapidly come back to haunt Mbeki because the Zuma-dominated ANC national executive committee has resolved to conduct a wide-ranging probe into the arms deal. This committee examining all aspects of the deal, until now something fiercely resisted by Mbeki, includes Mathews Phosa and Cyril Ramaphosa. The hunter has suddenly become the hunted.

The crucial factor will now be how such personal vendettas are contained. This is where Mbeki's bid for a third term as party president was so ruinously ill-conceived.

He's been at pains to prove that SA, under the ANC, will not become another dysfunctional African state, with leaders who cling obstinately to power. Recently, President Paul Biya of Cameroon, already in power for 25 years, said he intended to amend the country's constitution to allow him to remain in office after 2011.

"There have been appeals from deep inside the country for me to modify the constitution," Biya said ­ an explanation remarkably similar to Mbeki's claims that he was only standing for a third party term because that was the entreaty.

It is curious how those leaders who are most unsparing with racial accusations suddenly but invariably find at election times that there is simply no one else clever enough, experienced enough, or even capable enough, to take their place.

If I, as a white man, were to say that a black leader should stay on and on in power because there were no other Africans fit to take his place, Mbeki would denounce this view as racist and demeaning to Africans. Mbeki has often, rightly, been acerbic about white attitudes. But he has also seen conspiracies, slights and insults where others saw none at all. Thus Mbeki surveyed his fellow cabinet ministers and ANC colleagues and ­ yes! ­ felt he could not entrust one of them to lead the party.

This delusion warps most politicians who remain in power for a decade or so: Margaret Thatcher and Tony Blair spring to mind. In both those cases it was pressure from party bigwigs that forced the change. With Mbeki, in a triumph of far greater democracy, it was the ANC grassroots and popular sentiment that ensured his defeat.

Yet it is ironic that in many ways Zuma is Mbeki's shadow: a peasant populist against the urbane sophisticate. Zuma is accused of corruption in the arms deal, yet that is probably only a crumb *1 from the sticky cake of armaments sleaze Mbeki has presided over as president. Zuma took a shower after unprotected sex with an HIV-positive woman; Mbeki has poured cold water over the whole AIDS crisis with his bizarre pseudoscientific equivocations.

The crucial question today about Zuma is less what he's done privately, however utterly inappropriate, and what he intends to do publicly. Yet with our next president not chosen until next year, don't get carried away with only today's headlines.

When Sampson's biography of Mandela was published, I noticed in a footnote (page 629) that Ramaphosa, the man most famously diced by Mbeki, confided to Sampson in a private conversation that he intended to make a comeback to politics in 10 years. Okay, that was 12 years ago. But now the prey has turned hunter.

* Rostron is a freelance writer.

With acknowledgements to Bryan Rostron and Business Day.