Okupe also said that no election has been free and fair in Nigeria since 1959 to 2018.
Last week, Mantu revealed in an interview on Channels Television that he paid electoral officials and security operatives to manipulate elections in favour of Peoples Democratic Party (PDP) candidates.
Reacting to the controversial confession, Okupe said all political parties in the country, including the ruling All Progressives Congress (APC), are guilty of election malpractices, adding that all elections - past and present - are rigged.
He said Mantu "spoke as a true compatriot" and should not be misrepresented.
Okupe stated this on Monday, April 2, 2018, via his Facebook page.
He said, "For the avoidance of doubt, ALL elections are RIGGED in Nigeria from 1959 to date, without ANY exceptions.
"This rigging is all-encompassing and involves all political parties from action group, NCNC, NPC to NRC, SDP, PDP, AD, ACN, CPC AND APC.
"If anyone says anything to the contrary, such persons are wilfully perjured individuals and the true enemies of progress in Nigeria. Mantu spoke as a true patriot who desires true and genuine change.
"Suddenly the substance of his honest disposition is lost to partisan blame game that has not advanced our course of history in any way.
"People like Ibrahim Mantu and late President Yaradua who even openly admitted that the election that brought him to power was faulty, are heroes of this country."
Okupe said all governorship elections in the country won by the ruling party buttressing that the polls are rigged to favour the incumbent power.
"How can anybody claim that only PDP rigs elections in Nigeria?" he asked.
"Parties in Nigeria rig both intra and interparty elections from wards through local governments all the way to National elections from time immemorial.
"Are we not witnesses to the undeniable fact that in all state elections, no matter how civilized, innocuous or God-fearing the state governors pretend to be, all state elections, No matter the political party involved, are won by the ruling party in the state 100%.
"For a truth, it is only in the southwest and a few other zones that a modicum resemblance to an election actually do take place. in most other parts of the country. Nothing like elections take place or better still the charade of people lining up and casting their votes is just a mere ritual that has nothing to do with the results announced.
"It is in our overall interest that we take what Mantu said seriously and for posterity sake, let us sit down and plan how to conduct proper free and fair elections in our country. Democracy is mocked if people have the right to vote but their votes do not count."
The PDP, however, has distanced from Mantu's confession, claiming that the politician did not rig election for the party but in his personal capacity.