The by-election contest has narrowed down to three candidates and analysts say the mini poll will be a litmus test for the county's political bigwigs.
Stakes are high as different camps rush to make their final submissions to the voters after nearly 10 weeks of political campaigns in the county’s eight constituencies.
Machakos County, which is widely considered the lower Eastern’s economic and political capital, has about 624,000 registered voters, according to data in Independent Electoral and Boundaries Commission's (IEBC) website.
Mavoko is the county’s most populous constituency with 118,180 registered voters, according to a voters' list published by IEBC in 2017.
It is followed by Machakos town with 109,877 and Mwala with 81,273 voters.
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Yatta comes fourth with 73,940, followed by Matungulu with 66,611, Masinga with 61,989, Kathiani with 54,909 and Kangundo with 53,475 voters.
The three leading candidates are Urbanus Ngengele of United Democratic Alliance (UDA), former Cabinet Minister Mutua Katuku (Maendeleo Chap Chap) and Agnes Kavindu (Wiper).
Ngengele has the support of former Machakos senator, Johnstone Muthama, who is the interim chair of UDA, a relatively new political outfit associated with Deputy President William Ruto.
Katuku is being backed by Maendeleo Chap Chap party leader and Machakos governor Alfred Mutua.
On the other hand, Wiper party leader Kalonzo Musyoka has been pushing for the election of Ms Kavindu, who is Muthama's former wife.
Ruto, Mutua and Kalonzo have all declared interest in the presidency in next year’s General Election and their individual performance in the mini poll could be used as a yardstick for their popularity.
The past few days have seen heightened political activity in the county, with different campaign teams intensifying their propaganda wars.
Religious leaders
Muthama, who is leading the campaign team for Ngengele, is desperate for a win.
He must prove his political influence as the UDA chair and especially in the political battle taking place in his backyard.
The former senator has been telling voters to elect Ngengele in the spirit of Hustler Movement, claiming that the other candidates are not capable of safeguarding the interests of Machakos residents.
“If you elect Ngengele, you will have two senators. While he (Ngengele) will be representing the people in the Senate, I on the other hand will be "senator on call" to attend to any emerging issue that may face Machakos residents,” Muthama said during a recent political rally to drum up support for Ngengele.
Muthama, who declared himself the new Ukambani political kingpin after a fall-out with Kalonzo, pleaded with voters not to embarrass him by voting in a different candidate.
On the other hand, Maendeleo Chap Chap brigade led by Mutua has been mounting door-to-door campaigns for Katuku, with teams meeting thousands of focus groups in villages across the county.
In the Wiper camp, Kalonzo has marshalled the support of several MPs loyal to him as well as religious leaders to drum up support for Kavindu.
The former vice-president has been fighting off allegations by the opposing camps that his party’s choice of Kavindu was an attempt to settle political scores with Muthama