Madagascar's President Andry Rajoelina has registered his candidacy for July's election, despite previously insisting that he would not stand.
His name appears on a list released by the electoral authorities of 41 approved presidential candidates.
Mr Rajoelina, backed by the army, ousted Marc Ravalomanana from power in 2009, plunging the island nation into four years of political turmoil.
Under regional pressure, both men agreed not to contest July's poll.
But a special adviser to Mr Rajoelina said the deal was broken when Mr Ravalomanana's wife, Lalao, decided to stand.
"Now the competition is open to everyone," Augustin Andriamananoro told the Reuters news agency.
Mrs Ravalomanana returned in March from South Africa, where she and her husband fled after he was forced from power.
The authorities in Madagascar have blocked several attempts by Mr Ravalomanana to come back, citing fears of unrest.
Former President Didier Ratsiraka, 76, who went into exile for several years after losing a disputed election to Mr Ravalomanana in 2002, is also on the list of candidates.
Mr Rajoelina rose to prominence as a disc-jockey before entering politics.
The 2009 coup has left Madagascar isolated by the international community and deprived of foreign aid.