Muhammadu Buhari taking on incumbent Goodluck Jonathan.
The 71-year-old was chosen for the main opposition All Progressives Congress (APC) ticket, after an all-night vote by 7,214 delegates at a party convention in Lagos.
The 71-year-old was chosen for the main opposition All Progressives Congress (APC) ticket, after an all-night vote by 7,214 delegates at a party convention in Lagos.
His most prominent challenger, former vice-president Atiku Abubakar, could only muster 954 votes and he conceded as Buhari's soared towards 3,000, with counting not yet finished.
"Congratulations General Buhari. The delegates have spoken, you fully deserve the victory," Abubakar said on his Twitter account @atiku.
Buhari ended up with 3,430 votes.
Jonathan, 57, was endorsed by his ruling Peoples Democratic Party (PDP) at a separate meeting in the capital, Abuja, on Wednesday night. No other candidate had challenged for the nomination.
- Front runner -
Last time round in 2011, Jonathan secured nearly 22.5 million votes or nearly 59 percent of the ballots cast.
Buhari, then campaigning for the Congress for Progressive Change, scored 12.2 million or nearly 32 percent.
The vote on February 14, 2015 is expected to the closest since Nigeria returned to democracy 15 years ago, with the opposition -- a coalition of four parties -- stronger than ever.
Buhari has a reputation for cracking down on corruption from his time in power and the APC has campaigned hard on what it sees as Jonathan's lack of action against high-level graft and impunity.
As a former general, he is also expected to be better-placed to tackle the Boko Haram insurgency, which critics say Jonathan has been unable -- or even unwilling -- to stop.
In a sign of the almost daily violence in the troubled north, two female suicide bombers on Wednesday detonated their explosives at a crowded textile market in the northern city of Kano.
Four people were killed and seven others injured, according to the police.
Signs that Buhari would clinch the nomination came in the early hours of Thursday as the five candidates gave speeches to delegates.
Buhari, wearing an embroidered APC cap, won the loudest cheers as he took the stand and he appeared well in the lead after counting got under way from about 9:00 am (0800 GMT).
- Strong following -
Commentators saw Buhari's closeness to the APC's political godfather Bola Tinubu as a strong indication that he would win, as well as the perceived drawbacks of Abubakar.
Abubakar, 68, was vice-president for eight years under president Olusegun Obasanjo and is a consummate political operator but has been dogged by persistent allegations of corruption from his past.
That would have made his candidacy hard to support for a party campaigning against corruption, even if Buhari is seen as lacking clear ideas on wider policy and an appetite for day-to-day politics.
Buhari, who also lost to Jonathan's predecessor Umaru Musa Yar'Adua in 2007 and Olusegun Obasanjo in 2003, has a wide following in the Muslim-majority north.
He may benefit from a more well-organised party machine than last time round.
But the APC has voiced concerns about whether the vote will even hold in areas of the northeast blighted by Boko Haram violence, which they warn could cast doubt on the overall result.
