Three contestants, including the incumbent, Mr Akinwunmi Ambode, are in the race.
Hamzat made his decision known on Saturday at a press conference at the Ikoyi residence of Sanwoolu, declaring that he took the step because he strongly believed that he (Sanwoolu) possessed what it takes to rule Lagos in 2019.
The press conference was attended by Sanwoolu, his campaign director-general, Mr Tayo Ayinde, Otunba Lekan Osifeso and Dr Ibijoke, wife of Sanwoolu.