Governor Alfred Mutua has dismissed his rival's allegations that there was a plot to burn the county government's offices and asked police to boost security at the premises.
Dr Mutua on Friday wrote to Deputy Inspector General of Police Samuel Arachi, asking him to investigate Ms Wavinya Ndeti over her claims that he was plotting to burn crucial government documents to interfere with investigations into graft allegations.
The governor said: "All organs of security should be mobilised to thoroughly and speedily investigate the arson allegations made by Ms Ndeti to deter any terror attacks on my government."
Ndeti last week wrote to the police claiming that the governor was plotting to burn down the county property to thwart criminal investigations into corruption allegations.
But Mutua dismissed the claims and is now instead asserting that his rival could be planning to torch the property and blame it on him.
Mutua said he has always been open to investigations by independent agencies and that the claims could only mean that Ndeti was behind the arson plot.
"The sensational claim of arson in Ms Ndeti's letters can only, therefore, be construed to mean that there could be such a political and criminal plan by her or her supporters to frustrate my government by burning the said buildings to justify the contents of the malicious letter so as to gain political mileage," said Mutua.
The Maendeleo Chap Chap leader will face off with Ndeti, who is running on a Wiper Party ticket, for the county's top seat.
Mutua also accused Ndeti of threatening to evict non-locals from the county, terming this unlawful.
The governor said the arson and eviction plots were a grave matter and asked the police to ensure the security of all the people in the county during the electioneering period.
"I would like to request you to join me in reassuring non-Machakos Kenyans working and residing in Machakos County that the plan by Ms Ndeti to evacuate them is not only unlawful but will also not be tolerated at any time," he added.
A grave matter
The county boss has written to the chairman of the National Cohesion and Integration Commission, Francis ole Kaparo, and the chief of the Independent Electoral and Boundaries Commission, Wafula Chebukati. He also wrote to the chief prosecutor of the International Criminal Court, Fatou Bensouda.