Nigerian President Muhammadu Buhari will run for re-election in February 2019 against former vice president Atiku Abubakar, a Muslim from the country's north who was nominated on Sunday as the main opposition party's poll contender.
Buhari, a 75-year-old former military ruler, was the sole candidate for his ruling All Progressives Congress (APC) party, so his confirmation by some 7 000 delegates gathered in the capital Abuja was a mere formality on Saturday.
The APC swept to power in 2015 with the first opposition victory at the ballot box in the country's history.
But next year's presidential race appears to have tightened in recent months with the APC hit by a wave of defections over Buhari's leadership style.
On Sunday, delegates to a weekend convention of the former ruling Peoples Democratic Party (PDP), nominated Abubakar, 71, as his challenger for next years poll.
The politician and business tycoon has made four previous attempts at the top job in Nigeria, Africa's most populous nation.
Abubakar comes from the Muslim-majority north, and his nomination follows an unwritten rule in Nigeria that the presidency should alternate every two terms between a candidate from the north and south.
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The PDP vote was held in the oil hub of Port Harcourt, in the heartland of the southern Niger delta.
Abubakar garnered 1,532 votes, far outstripping his closest rival Aminu Tambuwal, the governor of northern Sokoto state who scored 693 votes.
The Eurasia Consultancy group said Saturday the outcome of the PDP primary would determine whether Buhari "loses his incumbency advantage", adding that Tambuwal would be the "strongest challenger".
Port Harcourt streets were festooned with conference banners, while police said thousands of officers were deployed to the PDP primary.
Despite humble beginnings in northern Nigeria, Abubakar rose through the ranks of the customs service for two decades, to eventually become the institution's number two during military rule.
The position is thought to have brought him enormous wealth but he then entered the private sector, investing in oil services and agriculture, among other industries.
From there he joined the civilian government where he became one of Nigeria's most recognisable and enduring politicians.
But his official, political and family life has been dogged by controversies ranging from his numerous wives and more than 20 children to allegations of corruption.
'Baba Go Slow'
Buhari indicated in April that he planned to run for a second term.
After running unopposed at the APC convention, "his name shall be forwarded to the Independent National Electoral Commission as the candidate of the party in the 2019 presidential election," said Kayode Fayemi, governor-elect of southwestern Ekiti state.
The retired general, who headed a military regime in the 1980s, has faced growing pressure to step down because of failing health after spending several months in London last year treating an undisclosed ailment.
Dubbed "Baba Go Slow" because he took six months to appoint cabinet ministers, he has also faced attacks for his handling of the economy, which plunged into recession in 2016.
He has also come under criticism on security issues, including the Boko Haram insurgency in the northeast, long-running farmer-herder clashes in the centre and militancy and kidnapping in the south.
"The fact that nobody came forward to challenge the president is an indication that the party members are satisfied with his performance and they want to see more of him in office," presidential spokesperson Garba Shehu told AFP.
Nigerian law allows for a president to serve a maximum of two four-year terms.
Voters in the former British colony will elect governors and lawmakers as well as the president in elections set for February and March next year.