Other members of the PDP also in the race include Aminu Tambuwwal, Sule Lamido, Kabiru Turaki, Attahiru Bafarawa, Datti Baba-Ahmed, Ahmed Makarfi, Jonah Jang and David Mark.
Officials said at least 4,000 delegates from the 36 states and the capital Abuja were expected to vote at the PDP primaries in the oil hub of Port Harcourt, in the heartland of the Niger delta, in an event due to extend to Sunday.
Atiku Abubakar won on Sunday nearly half the votes cast in a primary race to become the main opposition challenger to Nigerian President Muhammadu Buhari in next year's elections, party officials said. Atiku and Saraki, coming second place, had a total of 11 per cent, while Kwankwaso staggered behind with a slightly lower percentage of 10 per cent.
Jonathan also appealed to delegates to choose rightly even as he commended the spirit of sportsmanship of the aspirants for choosing to support whoever emerged as the party's presidential candidate.
"I want to pay tribute to each and every one of them assure you that I am ever ready to work with each and every one of them for the realisation of the victory of our party in the forthcoming elections".
"We are with you and confident that with us as a team May 29 2019 will be a day that our party will take over".
" As former Speaker House of Representatives, what we did still speaks volume".
Nigerians on social media are trolling the Senate President for not winning the primary election after putting in some much efforts.
In their reactions, some Nigerians believe Mr Abubakar is a worthy candidate able to challenge President Muhammadu Buhari in next year's election; others, however, say a younger and "less corrupt" candidate would have been a better option.