I'm sure that voting being extended to a second day plays a role. The center-right New Patriotic Party demandid a vote audit, and audited data from the biometric verification machines. From AFP (France): "Ghana's main opposition party on Sunday alleged a 'pattern of fraud' in the country's tight presidential election, saying it had evidence that its candidate Nana Akufo-Addo had won the vote. The opposition's claims came as partial official results showed the race almost neck-and-neck, while local media gave incumbent John Dramani Mahama a slight edge based on provisional results from nearly all districts. Ghana, a new oil producer with a booming economy, is seeking to live up to its reputation as a beacon of democracy in turbulent West Africa."
The New Patriotic Party is crying foul: "Privately owned Joy News television, based on provisional results from 269 of 275 districts, said Mahama of the NDC party had garnered 50.66 percent of the vote and Akufo-Addo 47.76 percent. The electoral commission was releasing results on its website, but the most recent numbers available included only 173 of 275 districts. Those results put Mahama at 49.61 percent and Akufo-Addo at 48.9 percent. A run-off election is to be held on December 28 if no candidate receives more than 50 percent. There are a total of eight presidential candidates."
Center-rightists have quietly taken to the streets: "'We call upon our party members and the general public to ignore the tainted provisional results announced through the mass media,' the NPP said. A crowd of about 200 NPP supporters sought to march on the electoral commission Sunday afternoon. They remained peaceful as they stood behind security forces who blocked a main road to the commission, shouting 'we want justice,' an AFP correspondent reported."