BOUREIMA BALIMA IN a year marked by setbacks for West African democracy, Niger is poised to hold an election on Sunday that will lead to the country's first transition of power between two freely elected presidents. President Mahamadou Issoufou is stepping aside after two five-year terms, in contrast to leaders in Ivory Coast and Guinea who used constitutional changes to extend their tenures to three terms. That represents a milestone for Niger, which has experienced four coups since gaining independence from France in 1960. The practical significance, however, is less clear. Mohamed Bazoum, Issoufou's handpicked successor and the favourite in…