Voters in Guinea-Bissau go to the polls shortly to elect a new president to replace Malam Bacai Sanha, who died in January following a long illness.
Nine candidates are running for office, but analysts say only four have a fighting chance.
The West African country has been plagued by army mutinies and coups over the past 10 years.
No elected president has completed his mandate since multi-party politics was introduced in 1994.
Several senior military figures are accused of involvement in the international drugs trade and the country has become a trafficking point for cocaine from South America to Europe
The BBC's John James in Guinea-Bissau says the big test is whether the winner will be acceptable to the losing parties and the armed forces.
Carlos Gomes Junior, 60, has stepped down as prime minister to run as candidate for the governing African Party for the Independence of Guinea and Cape Verde (PAIGC).
The three other candidates expected to do well are Kumba Yala, who was president from 2000 to 2003; MP Manuel Serifo Nhamadjo and former businessman Henrique Rosa.
The election in the former Portuguese colony is being overseen by about 180 foreign observers.
UN Secretary-General Ban Ki-moon and the US have called for a peaceful, orderly and transparent election on Sunday.
Malam Bacai Sanha was elected president in 2009 after years of unrest and coups.
His predecessor - Joao Bernardo Vieira - was assassinated by mutinous soldiers.
Last December the US warned its citizens in Guinea-Bissau that there was increased potential for political instability and civil unrest.