President Thabo Mbeki has moved another step closer to ending South Africa's most intense political crisis by appointing Phumzile Mlambo-Ngcuka deputy president.

But after weeks of tension in the ruling tripartite alliance, Mbeki's move to bring stability back to his government has inevitably set off a fresh round of speculation and criticism.

In deciding on a successor to former deputy president Jacob Zuma, Mbeki will have carefully considered any possible fall-out from his decision, not least of which would have been the reaction from Zuma's supporters.

One pressing thought on the minds of Zuma's allies is Mlambo-Ngcuka's relationship with Bulelani Ngcuka, the former national director of public prosecutions.

It has been three weeks since Zuma's financial adviser, Schabir Shaik, was convicted by the Durban High Court of corruption and fraud, setting the stage for Mbeki's dramatic axing of the country's second most powerful politician.

Since Zuma's dismissal last Tuesday, the ANC has announced that Zuma, after being informed that he was to be charged with corruption, has withdrawn from active politics. This move, announced late on Monday, surprised even Zuma's closest allies in Cosatu and the SA Communist Party.

Of huge significance was ANC spokesman Smuts Ngonyama's suggestion that Zuma would not even be able to speak on behalf of the organisation he had served diligently for 47 years.

Equally astonishing was the ANC's strongly worded statement, issued after a national working committee meeting that Zuma did not attend, that effectively lambasted Zuma and his allies for claiming the former deputy president was the victim of a political plot.

Yesterday, the government's chief spokesman, Joel Netshitenzhe, took a similarly hard line when asked whether Mlambo-Ngcuka's appointment would not fuel the allegations of a "political conspiracy".

While most of the ruling alliance publicly welcomed Mlambo-Ngcuka's appointment, there were rumblings about the president's choice as his new deputy being married to Bulelani Ngcuka, the man who subjected Zuma to a media trial by calling a press conference on August 23, 2003, to say there was a prima facie case of corruption against Zuma, but charges would not be brought against him.

As it turns out, Zuma is to have his day in court, but only after three years of intense public scrutiny.

And, as Netshitenzhe pointed out yesterday, Mlambo-Ngcuka's success can hardly be credited to her husband - she is a competent and skilful politician who has risen through the ranks by sheer dedication and hard work.

Supporters of Zuma, however, continue to see the former deputy president's fall from grace as part of Mbeki's master plan to choose his own successor.

They also see Mlambo-Ngcuka's appointment as an "insensitive" slap in the face for Zuma, possibly some sort of reward for the "prima facie" statement.

The flipside of the coin is that there is an underlying presumption that South Africa is indeed in the midst of a great conspiracy to get rid of Zuma, implying that Justice Hilary Squires's finding that there was a "generally corrupt relationship" between Shaik and Zuma is also part of that plot and that the separation of powers between the executive and the judiciary has been flagrantly violated.

Of concern to insiders is Zuma's stint as head of ANC intelligence and his reputation for being a no-nonsense cadre of the liberation movement.

With this in mind, Mbeki's decision will also have taken account of the succession debate within the ruling alliance and the much-vaunted possibility that the person appointed to replace Zuma will have to contend with speculation that the incumbent is Mbeki's choice to succeed him when he steps down as president in 2009.

But Mlambo-Ngcuka has not been seen as a contender for the post of ANC president at the party's 2007 national conference. As some in the ANC have noted, she is not considered as senior as other possible candidates.

Her appointment has also raised questions about her involvement in the "Oilgate" allegations, but Mbeki will have taken this into account and he would have had to be certain that she had no part in what might yet prove to be a scandal.

With acknowledgements to Jeremy Michaels and the Cape Times.