Gbadebo Rhodes-Vivour won the Lagos State Labour Party (LP) governorship substitution primary election on Wednesday in Ikeja, Lagos.
Mr Rhodes-Vivour, who defected to the party last month from the PDP, polled 111 votes while his opponent Moshood Salvador got 102 votes.
Mr Salvador also defected to the party from the APC last month.
The party had, however, held its primaries months ago in which Ifagbemi Awamaridi, the state chairperson, emerged the guber candidate.
Mr Awamaridi, who has been recognised by INEC as the Labour Party guber candidate in Lagos, has said he would not withdraw his candidature.