Ashok Kumar Saroj was shot dead night while he was returning home from Ramganj market, they said.
Scores of his supporters staged protest and blocked the Ramganj-Gyanipur road here, they said.
Additional police forces and PAC have been deployed on spot to avoid any untoward incident and efforts are on with district administration to bring the situation under control, police said.
Saroj had unsuccessfully contested the last Zila panchayat polls from Gyanipur.