Mantu, who pronounced himself as a born-again politician in 2017, said he also bribed agents of other political parties.
Mantu revealed that he gave money to officials of the Independent National Electoral Commission (INEC) and security operatives to manipulate elections in favour of the PDP.
He disclosed this during an interview on a Channels Television programme, Hard Copy.
On how he rigs elections, he said, "I don’t have to go and change election (results) but when you provide money, you give money to INEC boys that if they see any chance they should favour you, you provide money to the security (personnel); I tell you it’s not necessarily when I am contesting election but when my party sponsors a candidate, I will like that candidate to win election."
Mantu, who pronounced himself as a born-again politician in 2017, said he also bought the loyalty of agents of other political parties in order not to raise any objection to the outcomes of the elections.
The politician commended the current PDP chairman, Uche Secondus, for apologising to Nigerians for the party's past mistakes.
He advised other politicians to repent from electoral malpractice and urged Nigerians to vote wisely in 2019.
"I am tired of living in poverty in the midst of plenty and I believe that we have the resources that people can live a decent life without being beggars to those who have.
"So we need good governance and good governance can only be provided by good people; good people who are truly repentant, who are concerned about the well-being of the people", he added.
The PDP, which held power for 16 years, has been at loggerheads with the ruling All Progressives Congress (APC), which took over power in 2015, over who is the most corrupt party.
On Monday, March 26, 2018, PDP chairman, Secondus apologised to Nigerians for impunity, imposition of candidates and other mistakes made by the party in the past.
Speaking at a public national discourse on 'Contemporary Governance in Nigeria', he said, "I hereby, as the National Chairman, do admit that the PDP made a lot of mistakes.; we are humans, not spirits and the ability to admit is key in moving forward.
"We admit that we have made several mistakes; we have passed through all our challenges and have acquired the experience no other party can boast of.
"We were sanctioned by Nigerians at the polls in 2015; let me use this opportunity to apologise for our past mistakes.
"It is the honest thing to do, a legacy to transfer to our children; we cannot continue like that.
"When we make mistakes, we should come out boldly to the people and apologise."
Reacting to the apology on Thursday, a national leader of the APC, Asiwaju Bola Tinubu advised Nigerians not to accept the apologies tendered by the PDP.
Tinubu stated this at a colloquium organised to mark his 66th birthday in Lagos.
He said the apologies is deceitful and an attempt to hoodwink Nigerians to get a political advantage ahead of the 2019 elections.
Tinubu added that the PDP brought the country to its knees with massive corruption, saying they should not be allowed to return to power again.