The race for the presidency of Zanzibar had by Friday attracted 11 candidates, two of them sons of former presidents.
Ali Karume, 70, son of Zanzibar's first president Abeid Amani Karume, will face off with Hussein Mwinyi, 53, whose father, Ali Hassan Mwinyi led Zanzibar from 1984 to 1985, before succeeding Julius Nyerere as Tanzanian president from 1985 to 1995.
Mr Karume, who is also the younger brother of former Isles president Amani Abeid Karume (2000-2010), has served as Zanzibar's ambassador to several European countries.
Zanzibar's president comes third in the hierarchy of power between Union and Isles’ government.
Other contenders are Makame Mbarawa, the current Minister of Water in the Union government; Zanzibar's current Minister of Information, Tourism and Heritage Mahmoud Thabit Kombo; and former Zanzibar chief minister Shamsi Vuai Nahodha.