Amid tight security arrangements, polling commenced this morning for the bypolls to the Hisar Lok Sabha seat, which is witnessing a triangular contest. The Anna factor is looming large in the constituency raising the stakes for the ruling Congress.Polling began at 8 AM and will continue till 5 PM. The seat fell vacant after the death of former chief minister and Haryana Janhit Congress leader, Bhajan Lal in June.