Dosunmu contested the Lagos governorship primaries in 1999 but lost to Senator Bola Tinubu.
He won the seat for the Lagos West Senatorial District on the platform of Alliance for Democracy (AD).
Later, he defected with some other AD federal lawmakers to the Peoples Democratic Party (PDP).
During the 1990s, he was prominent in the struggle to enthrone the presumed winner of the June 12 presidential election of 1993, MKO Abiola.
Dr Wahab Dosunmu, was a political activist and a chieftain of the National Democratic Coalition (NADECO) The late politician was one of those who fought for the actualization of the June 12, 1993 presidential mandate of late Chief M.K.O Abiola through NADECO.