John Atta Mills, the president of Ghana, died yesterday somewhat unexpectedly, leaving Ghana’s future less clear in advance of December’s presidential election.

His vice president, John Dramani Mahama, has been sworn in as his replacement, and according to the Daily Graphic, will likely be the presidential candidate of Mills’s National Democratic Congress in December.

A longtime crusader for constitutional reform in the West African country of nearly 25 million people, and a symbol of a peaceful, democratic tradition still relatively rare throughout sub-Saharan Africa, Mills was elected in December 2008 in a very close election against Nana Akufo-Addo.

Mills, a quiet-mannered law professor, previously served from 1997 to 2001 as vice president to Jerry Rawlings.  Rawlings initially took power in a 1979 coup, but subsequently retired from the military and managed Ghana’s largely successful transition to democracy following a 1992 constitutional referendum.  He was elected president in his own right in 1992 and 1996.  That transition, two decades years ago, has held up relatively well — Rawlings transferred power peacefully to his political rival, John Kufuor, in 2001, who transferred power peacefully in 2009 to Mills.

The strength of Ghana’s institutions was on display yesterday, with no significant hitches in Mahama’s swearing-in:

Analysts took that smooth transition as reassurance of the robustness of Ghana’s institutions. “The constitutional process kicked into gear pretty well,” said Antony Goldman of the Africa-focused group PM Consulting. Razia Khan, head of Africa research at Standard Chartered bank, said: “The smooth inauguration of Mahama as President is an encouraging sign of strength of Ghana’s democratic institutions.”

Mills oversaw the first-ever oil production in Ghana in 2010 on the appropriately-named Jubilee oilfield, which has sparked maginificent double-digit growth rates — Ghana’s economy previously rested on gold mining, cocoa and other exports.  While its GDP per capita (even with newly discovered oil reserves) remains small in comparison to South Africa or Botswana  — or even Angola — Ghana has outpaced per capita GDP per capita of other West African countries like Sengal by 150% and countries like Mali and Burkina Faso by 200% to 300%.

In contrast to other countries in sub-Saharan Africa, including neighboring Côte d’Ivoire, Ghana has not been torn apart by ethnic or sectarian or tribal strife.  Unlike central and southern Africa, it does not have outrageously high HIV/AIDS rates and life expectancy lags not far behind that in Europe or the United States.

The spotlight now turns to Mahama, especially if, as expected, he becomes the standard-bearer of the NDC, the party that Rawlings founded and the more social democratic of two major parties in Ghana (the other main party in Ghana’s two-party system is the more center-right New Patriotic Party of Kufuor and of Akufo-Addo).

Presidential and legislative elections are scheduled for December 7 of this year, with runoffs to follow as necessary on December 28.  Like in the United States (and unlike, say, parliamentary systems in Germany or the United Kingdom), Ghana’s president is both head of government and head of state, so the presidential race will be a huge prize.

Mahama served as a member of Ghana’s parliament from 1997 to 2009, and he also served as minister of communications from 1998 to 2001, where he helped to guide Ghana’s telecommunications industry after its deregulation in 1997.  As vice president, he has focused on environmental issues, especially as regards plastic waste.

As Les Roopanarine writes in The Guardian today, though, Ghana’s stability remains fragile after Mills’s very narrow election win four years ago:

Although the 2008 presidential election consolidated Ghana’s reputation as a stable democracy, it was a close-run thing. Tensions threatened to spill over when neither Mills nor his NPP rival [Akufo-Addo] secured a majority in the initial poll. The tightly contested runoff was accompanied by allegations of vote-rigging, highlighting Ghana’s ethnic divisions and leaving the country on a knife-edge.

December’s election — an anticipated rematch between Mills and Akufo-Addo was already going to be close.  Mills’s passing won’t change that.