With cases of voter identification devices failing, voting in Baringo South mini-poll began early Friday to a slow start.
The faulty Kenya Integrated Management Systems (KIMS) kits were reported at Marigat Boys High School and Kimorok Polling Station.
Electoral officials say the turnout so far has been low but remain optimistic it will balloon later in the day.
The seat fell vacant following the death of Grace Kipchoim in April of cancer.
Ms Kipchoim who was serving her second term was bed-ridden in the run-up to her victory and did not conduct even a single rally in the highly-contested election.
Charles Kamuren of Jubilee party, Dr Cynthia Kipchilat (Maendeleo Chap Chap) and Paul Motoloi of Chama Cha Mashinani (CCM) are in the race to succeed her.
Kamuren and Kipchilat ran in the August 2017 General Election.
Just last week, Sylvester Sergon of Republican Liberty Party dropped out of the race to back Dr Kipchilat, a move many political pundits say reduced the contest to a two-horse race race between Maendeleo Chap Chap's Kipchilat and Jubilee's Kamuren.
Kipchilat, the only woman in the race, holds a Doctorate in International Business from the University of Florida in the US, and is a former lecturer at Egerton University.
Mr Kamuren is a former Baringo Kenya National Union of Teachers secretary and a Kanu nominated MCA in the first Baringo County Assembly.
There are 35,162 registered voters in the constituency and 132 polling stations