Ghana’s general elections last week, the eighth since 1992, ended peacefully and affirmed the country’s credentials as a stable democracy in a West Africa region notorious for violent elections-related conflicts.

This time, however, the results were so close they threatened to end the second four-year term ambitions of President Nana Addo Dankwa Akufo Addo and his New Patriotic Party (NPP) government. The main opposition New Democratic Congress (NDC) and its presidential candidate, former president John Mahama, contend the close results show they won, suspecting fraud, and have called for an investigation...