A councillor candidate, who won the election in the Sirajganj municipality, was stabbed to death by miscreants while celebrating victory on Saturday night.   The deceased was identified as Tariqul Islam, 35, a councillor candidate of ward 6 and son of Abdul Kuddus of Bhangabari area of Sadar upazila.   Bahauddin Faruki, officer-in-charge of Sadar Police Station, said, Tariqul was elected unofficially in the municipality polls held Saturday.