The seat is currently held by Ms Cecily Mbarire who chose to contest the governorship position.
Elsewhere in the county, Mr Muriuki Njagagua is poised to retain his Mbeere North parliamentary seat.
With over 97 per cent of the 40,895 votes tallied, Mr Njagagua leads with 25,414 votes.
His closest challenger, Independent candidate Geoffrey Ruku, has 10,853 votes.
Also in the contest is Dr Patrisio Njiru (of Maendeleo Chap Chap, 3,022 votes)