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.
The 55-year-old former minister, who was also the World Bank's vice president for Africa from 2007 to 2012, said in a statement that Nigeria was becoming "a country where the worth of life is trending down to zero".
The respondents had an option of choosing between Dankwambo, former Vice President Atiku Abubakar, Senate President Bukola Saraki or Sen.
The party led by Buhari, who is seen as an anti-corruption crusader in graft-tainted Nigeria, swept to power in 2015 with the first opposition victory at the ballot box in the country's history. It is not a one man's job, it is a collective responsibility and I am prepared to listen to you, to take your advice, consult with you, work with you and together, we'll succeed and after we succeed, we shall all be partners in that success. We all knew right from the beginning that only one person will emerge so this is not a surprise to us.
Gary Neville fumes over Man United conduct regarding Mourinho leak
Mourinho claimed after the 3-2 home victory over Newcastle that he was the subject of a "manhunt". With the global break now taking effect, United do not play their next match for two weeks.
I also thank the well-deserved presidential candidate of our party.
"Sir you said yourself, this has been a journey, but you stayed on course and today you truly deserve this".
The former vice president scored 1,532 votes, more than double that scored by his closest challenger, Aminu Tambuwal, who had 693 votes.
Daily Trust learnt that delegates were said to be richer with some hard currencies from presidential aspirants.
Theresa May to tell conference
In a message to voters tired of belt-tightening, the PM said: "Because you made sacrifices, there are better days ahead". May's unexpectedly disarming conference speech followed, exhorting the party to come together, or Brexit is at risk.
Political analysts have already dubbed the emergence of the two formidable candidates as standard bearers of the two mega parties as battle of political Titans.
The poll asked, "Who is the best candidate for @OfficialPDPNig [PDP]?"
Aisha Buhari, wife of Nigerian president Muhammadu Buhari has censured the ruling All Progressives Congress, APC, over what she says was the rule by impunity and manipulation. "Simply put, in the PDP Presidential primary, every vote counted".
Will Modi-Putin handshake annoy Trump?
India signed an agreement for the purchase of S-400 air defense systems from Russia, Kremlin spokesman Dmitry Peskov said Friday. The pact was signed during talks between Indian Prime Minister Narendra Modi and visiting Russian President Vladimir Putin here.