Rebel governors who defected from Nigeria's ruling party have merged their splinter group with the main opposition party, eroding the power base President Goodluck Jonathan would need for re-election.
Seven governors from Jonathan's party have defected and made the merger official on Tuesday in the most explicit internal threat to his assumed plan to run in elections in early 2015.
Governors are among the most powerful figures in Africa's largest oil-exporting country - some control budgets bigger than those of many African states - and their influence carries a great deal of weight in selecting presidential candidates.
However, some were due to leave office or represented states that Jonathan was unlikely to win, leading analysts to question how much effect they could have.
The seven governors and ex-presidential hopeful Atiku Abubakar formed the splinter group opposed to Jonathan in August.
All were present for the meeting where the decision was made to merge with the opposition party, the All Progressives Congress (APC), said Lai Mohammed, a spokesman for the APC.
Not a 'done deal'
But a spokesman for one of the seven, Governor Mu'azu Babangida Aliyu of Niger State, said that "he remains a member" of the People's Democratic Party, Jonathan's party.
Official sources close to another governor said the agreement was not yet a done deal, so another may also remain.
"After exhaustive deliberations, the two parties agreed to merge in order to rescue our fledgling democracy and the nation," said a joint statement, read out by Kawu Baraje, chairman of the splinter group, who is not himself a governor.
The PDP has been in power since shortly after the end of military rule in 1998, but it has increasingly been riven by internal squabbles.
Many northerners say Jonathan's running again would violate an unwritten PDP rule that power should rotate between the largely Muslim north and mostly Christian south every two terms.
"They have come to join the APC. The governors have all agreed. We believe they are all on board," Mohammed said.
Amaechi told Reuters by SMS text message that the splinter group had joined the APC and Baba Dantye, a spokesman for Kano state governor Rabi'u Musa Kwankwaso, also confirmed the move.
"It is a blow to the PDP in terms of prestige, but most of the departing governors were from states where the president polled badly in 2011 and would not have been expected to win," said Antony Goldman, head of Africa-focused PM Consulting.