The Orange Democratic Movement (ODM) candidate Ochilo Ayacko has won the Migori Senate seat.
Mr Ayacko trounced five other candidates after garnering 85,234 votes (57.7pc) with his closest opponent Mr Eddy Oketch getting 60,555 (40.99pc).
The former minister had already pulled a comfortable lead on Monday night with four out of the eight constituencies reporting.
The Senate by-election was marred by low voter turn out with only 38.02 percent of the 388,633 registered voters casting their ballots. Only 511 votes were rejected.
The county has eight constituencies, namely Uriri, Rongo, Suna West, Suna East, Nyatike, Kuria West, Awendo and Kuria East.
It is only in Uriri, the backyard of Migori Governor Okoth Obado, that Mr Oketch trounced Mr Ayacko. Mr Obado, now in remand following allegations that he plotted the murder of university student Sharon Otieno, had backed the youthful Mr Oketch before his arrest.
Other candidates who participated in the by-election are: Peter Jobando (Green Congress Party), Mr Solomon Hodo Rugaria (People’s Democratic Party), Mr Samwel Otieno (independent) and Mr Dickson Ogolla (independent).
Suna East Constituency
Ayacko (11,950); Oketch (8,297); Jobando (147); Ogola (121); Hodo (34); Otieno (20).
Suna West Constituency
Ayacko (13,335); Oketch (8,221); Jobando (55); Ogola (66); Otieno (23); Hodo (8)
Oketch (14,291); Ayacko (8,680); Ogola (77); Jobando (51); Hodo (24); Otieno (21)
Kuria East Constituency
Ayacko (4,961); Oketch (1,585); Hodo (79); Otieno (77); Jobando (68); Ogola (63).
Ayacko (12,904); Oketch (5,315); Otieno (194); Ogola (60); Jobando (44); Hodo (8)