What is this strange thing called the “top six” of the ANC? An historical accident of relatively recent creation, it is not mentioned at all in the movement’s constitution.

For most of the ANC’s history, there have been at most three key national positions: president, treasurer and secretary-general.

The deputy presidency was introduced only in 1958 as part of an exercise in ethnic, regional and generational rebalancing. Two years later, after the banning of the ANC, the exile movement was run by its deputy president, OR Tambo. While Tambo also became “acting president” in 1967, he retained the office of deputy president until 1985, when a still incarcerated Nelson Mandela was “elected” to this position.

The prominent position of secretary-general has changed just as much over the years. Walter Sisulu and Tambo held the office in succession in the 1950s before later ascending to the deputy presidency and presidency, respectively.

In 1991, Cyril Ramaphosa defeated both the incumbent Alfred Nzo, and Jacob Zuma, for the position. Kgalema Motlanthe and then Gwede Mantashe succeeded him, creating a new “tradition”: an unbroken succession of former National Union of Mineworkers leaders in the post. The position of national chairman was created only in 1991. The office has no obvious function other than as a parking space for those with long-term ambitions, but it nonetheless carries prestige and expresses “seniority”.

The treasurer-general post has become more important as “donations” have become the lifeblood of a spendthrift movement. Incumbents Mathews Phosa and Zweli Mkhize have had a higher profile, and greater ambition, than their predecessors.

Can the past of the top six tell us anything about the likely future of the current incumbents? Under Mandela, the presidency rose in status, in part because of the exile movement’s elaboration of a “Mandela myth”. The linkage of the position to the state presidency thereafter allowed the incumbent to combine state and party mechanisms of control. This means all eyes are now on this big prize.

The deputy presidency, by contrast, is important primarily as an ostensible stepping stone to the presidency. Thabo Mbeki followed this route, becoming ANC deputy president in 1994 and ANC president in 1997. But Mandela arguably only succeeded to the presidency in 1991 because Tambo was ill.

Walter Sisulu, the deputy elected in 1991, did not go on to become president. He was elevated to the position to stop a battle between the real contenders for presidential power: Mbeki and Chris Hani.

Jacob Zuma was probably elected deputy only because Mbeki believed he could destroy him before he could rise to the very top. Zuma may have made the same fatal misjudgment when he selected his deputy, Ramaphosa, at the Mangaung conference in 2012.

If Ramaphosa seizes the presidency in December, the “stepping stone” status of the deputy presidency will become firmly established.

Little wonder, then, that Mpumalanga chairman David Mabuza and NEC grandee Lindiwe Sisulu, among others, are fiercely jostling for this position: they hope it will take them to the very pinnacle of power five or 10 years hence.

Scrupulous historians will argue that none of this can ever prove the obvious falsehood that the deputy president of the ANC always rises to the presidency, or that such a trajectory is “an ANC tradition”. At the current historical conjuncture, however, the history of the ANC is far easier to change than its future.

• Butler teaches public policy at the University of Cape Town.