Constable Michael Ndirangu has been hospitalised with serious head injuries after falling off a car in Mlango Kubwa on Sunday, during Jubilee Party rally.
The police officer is attached to nominated MP Johnson Sakaja.
He was hanging on the side of Sakaja's car on Juja Road when he lost his grip and fell off the Toyota Land Cruiser.
Ndirangu was rushed to Radiant Hospital for initial treatment and later transferred to the Nairobi Hospital.