Rajinder Kumar was arrested from Gholia Khurd village near power plant, and a 12 bore pistol used in the crime was also recovered from him, police said.
A police team arrested the accused while he was waiting for a bus, they said.
Kumar along with his two associates had murdered the SAD Sarpanch Beant Singh on the night of April 5 at Manuke village over old enmity.
According to an FIR registered on the complaint of Surinderpal Kaur, mother of the village head, her son Beant Singh (26) was shot dead by the three bike-borne persons.