Former Nigerian President Olusegun Obasanjo's endorsement of his one-time rival Atiku Abukar's presidential campaign is a major source of debate in the country.

Some have dismissed it as irrelevant, while others believe Mr Obasanjo has just made President Muhammadu Buhari's bid for a second term in next year's election tougher.

Since stepping down in 2007, Mr Obasanjo has been a serial critic of incumbents and remains politically influential.

Each of the candidates he endorsed - Umaru Yar'Adua in 2007, Goodluck Jonathan in 2011 and Mr Buhari in 2015 - won.

But Mr Buhari's team is confident that despite a spate of defections to the opposition, he still has grassroots support, especially in the north and the south-west, to carry him to victory in the elections due in February.

Mr Buhari will be the candidate for his All Progressives Congress, while Mr Atiku will run under the banner of the People's Democratic Party (PDP).

Both parties have have just concluded their primaries at national and state level. So expect aggrieved politicians in both parties to switch loyalties in the coming months as they consider what is their best option of being elected to office next year.