Kenyan foreign minister Amina Mohamed, Chadian opposition politician Moussa Faki Mahamat and Senegal's Abdoulaye Bathily, currently the UN's special representative for Central Africa, are among the candidates for the AU chairperson's post.

Two other contenders - Agapito Mba Mokuy from Equatorial Guinea and Pelonomi Venson-Moitoi from Botswana - were among the candidates rejected by African leaders in July during a summit in Rwanda's capital Kigali. They failed to achieve the necessary two-thirds majority in the secret ballot.

"Black smoke billows from the 27th AU summit as no winner emerges," the AU chairperson's spokesman Jacob Enoh Eben tweeted at the time.

But now time is running out. Current AU chief Nkosazana Dlamini-Zuma will step down in January after refusing a second four year term in office.

Strong lobbying behind the scenes

Botswana's Venson-Moitoi is said to have scored the highest number of votes at the Kigali summit, but fell well short of the two-thirds majority needed. Long considered the favorite to take over from Dlamini-Zuma, some analysts think that she has fallen behind Kenya's Amina Mohamed.

"I imagine that Kenya for example has been making big promises to countries to support Amina Mohamed's candidacy", Andrew Weir, deputy editor of Africa Confidential magazine, told DW. "A country like Botswana would find it hard to do this kind of horse-trading, being a much smaller economy and being somewhat isolated down there in the south." 

According to the magazine, President Uhuru Kenyatta has appointed a team of seven ministers to run a lobbying campaign for Mohamed. The 55- year-old is a seasoned diplomat who has represented her country at the Kenyan mission in Geneva and served as the deputy director of the United Nations Environment Programme.

"Kenya is putting a lot of weight into it, it is calling in a lot of favours to get member countries to support her candidacy," Africa Confidential's Weir said.

Do French-speaking candidates have an advantage?

Kenya has already proven its clout at the African Union with its successful lobbying against the International Criminal Court at The Hague.

But Mohamed's election as chairperson is by no means certain. Traditionally, the chairmanship rotates between English-speaking and Francophone countries. In 2012, Anglophone Dlamini-Zuma replaced French-speaking Jean Ping. If the principle is observed this time around, the candidates from Chad and Senegal would have an additional advantage.

Critics however reject the idea that the rotational system should be the decisive factor to find her successor.

"While there is some validity to this principle so that all Africans have a buy-in, this should not be at the expense of choosing the best candidate. Moreover, strictly adhering to the regional principle could readily become a conduit for cronyism," Ethiopian civil society activist Abdul Mohammed wrote in the blog AfricanArguments.

With the race for the chairperson's post still open, many observers expect that lobbying efforts by the candidates' home countries will intensify ahead of January's vote.