By late 2005 a faction within the People's Democratic Party (PDP) — variously associated with Tony Anenih, Andy Uba and other Aso Rock principals — was openly campaigning for a constitutional amendment that would allow President Olusegun Obasanjo a third term. The vehicle was the National Assembly Joint Committee on the Review of the 1999 Constitution, chaired in the Senate by Ibrahim Mantu (Plateau Central) and in the House of Representatives by Aminu Bello Masari (Speaker). Of the 116 proposed amendments only one — the elongation of the presidential term from two four-year terms to two five-year terms (the 'Doctrine of Necessity 7' formula) — would have given Obasanjo a third bite.
A cross-party, cross-zone coalition emerged against the bid. Senate President Ken Nnamani (Enugu East, PDP) — Obasanjo's own party-mate — refused to use his casting vote in favour and insisted the chamber sit through public hearings. Senators Ibrahim Mantu (for) and David Mark (against) led the floor management; outside the chamber the campaign was led by Atiku Abubakar (then sitting Vice-President), Nuhu Ribadu's first EFCC and a coalition of civil-society groups including the Nigeria Labour Congress under Adams Oshiomhole, the NBA, and the Save Nigeria Group precursors. Press leadership came from The Guardian, This Day, Tell, Newswatch and the resurgent Sahara Reporters.
On 16 May 2006 the Senate voted by voice. The bill was defeated decisively. The House of Representatives followed within days with a similar rejection. The PDP convention that subsequently produced the Yar'Adua / Jonathan ticket was the immediate political consequence; the Atiku-Obasanjo rupture became the defining personal rivalry of the next decade.
Obasanjo has consistently denied, in interviews and in his three-volume memoir 'My Watch' (2014–15), that he personally orchestrated the bid. The contemporary documentary record — including the EFCC's later prosecutions of bribery allegations tied to the vote — places the operation squarely in his immediate political circle. The defeat preserved the two-term limit which has, in the twenty years since, defined every constitutional debate on tenure.