Aziz's biggest challengers are Ahmed Ould Daddah, head of the main opposition party, the Rally of Democratic Forces; Messaoud Ould Boulkheir, a parliamentary speaker and the candidate of the National Front for the Defence of Democracy, and Jemil Ould Mansour, leader of the Islamist party Tewassoul.
Talk of change
Sghaier Ould MBareck, a former prime minister, earlier this month announced that he was withdrawing his candidature to support Aziz, who overthrew president Sidi Ould Cheikh Abdallahi in the August coup.
In all, nine candidates are standing in the election, designed to restore constitutional democracy to the northwestern African country.
Aziz, a self-styled "candidate of the poor", told his supporters during campaigning that he would "put an end to the waste and all the shocks that have brought Mauritania to its knees after several decades of misrule".
Each main candidate has attempted to broaden their support base with talk of real change, economic and social progress and development in the largely arid nation on the southwestern side of the Sahara.