National Assembly Speaker Moses Wetang'ula has already voted at Namakhele Primary School Polling Station in Kabuchai Constituency.
The Senatorial by-election which is underway is so far experiencing low voter turnout in a county that has 646,612 voters.
The Independent Electoral and Boundaries Commission (IEBC) said stations opened at 6PM for voting and will remain open until 5PM.
The seat fell vacant after Moses Wetangula was elected as the National Assembly Speaker.
Azimio has fielded former Kanduyi MP Wafula Wamunyinyi, who will be the first person after Odinga to fly the coalition party’s flag.
According to IEBC returning officer Grace Rono, there are 1,373 polling stations adding that the county tallying center will be at Mabanga Agricultural Training Center (ATC).
She spoke Wednesday at the Bungoma County IEBC offices as she commended the aspirants for conducting peaceful campaigns asking them to ensure the same peace prevails during voting day.
She also dismissed claims of already marked ballot papers by one candidate, saying no papers had been marked.