Onitsha - PDP toppled the main opposition candidate in a state governorship vote this weekend, officials said, giving President Goodluck Jonathan a boost ahead of national polls next year.
Ayodele Fayose of The People's Democratic Party's (PDP) took almost 60 percent of the vote in southwestern Ekiti state, unseating the opposition incumbent Kayode Fayemi, the electoral commission announced on Sunday.
Governors are among the most powerful figures in Africa's largest economy and oil producer. Some control budgets bigger than those of many African countries and play a significant role in selecting presidential candidates.
The victory in Ekiti - where organisers said voting was fair and peaceful - was a rare piece of good news for a ruling party that is likely to see its sternest test yet in the 2015 national election.
Jonathan has been beleaguered by defections of senior figures and criticism for his government's failure to quell group Boko Haram, which abducted more than 200 schoolgirls from a remote northeastern village in April.
The main opposition All Progressives Congress (APC) was created out of four regional parties last year - presenting a nationwide challenge to the ruling party.
Fayemi took office in late 2010 after a court annulled the result of 2007 polls that were marred by intimidation, vote-rigging and ballot-stuffing.
Security was heavy during this year's polls, and the electoral commission declared the election "free, fair, credible and transparent".
The United States would be watching the vote with "great interest", Washington's ambassador to Nigeria, James Entwistle, said ahead of the polls, adding a free and peaceful election would help demonstrate the credibility of the electoral system.
More than 800 people were killed and 65 000 displaced in three days of violence following the 2011 presidential election, Human Rights Watch has said.
Rioting erupted mainly in the mostly Muslim north after Jonathan, a Christian from the south, won the vote.