Since Michael Sata's death the focus has been on his Patriotic Front (PF), and who it will put forward as its candidate in Zambia's presidential by-election that's meant to be held in January.

But the country's opposition parties are also in the throes of their own political game of chess. While the PF is expected to win, if the opposition can unite behind a single candidate, they could take power.

Former president Rupiah Banda is a central figure on the board. His biggest advantage is that everyone knows who he is, and that matters when there's only about 75 days to go until people vote. But he has to get around Nevers Mumba, the leader of his party, the Movement for Multi-Party Democracy.

Then there's the United Party for National Development's Hakainde Hichilema, a worthy opponent. But he's a Tonga and the country is majority Bemba, and to many, that matters.

I watched an interview with Banda just after Sata's death where he was coy about his presidential ambitions.

But when we met he was more direct, and on the subject of protests that broke out last week between rival PF factions he said: "It shows you our peace is brittle. I think it is important to emphasise to Zambians that we need to work towards unity.

"We have too many problems and they can't be overcome unless we work together. If I were to come back, this is one of the things that I would do."

While people queuing to see Sata's remains, constantly praise him for an ambitious infrastructure programme, bringing development to the rural areas, Banda said it was started under former president Levy Mwanawasa, continued by him and inherited by Sata.

Banda also endeavoured to trying to resolve the debate around the draft constitution and to "reopening" the country to investors. He's clearly on the verge of open campaigning.

But things are never simple in politics. Whoever wins the by-election will only be president until 2016 when Zambians will vote again, in their regularly scheduled elections.

If Banda wins in January it would count as his second term - and therefore his last. So if he were to stage a successful comeback to the presidency now, his victory would be very short-lived.