Mizoram’s opposition party Mizo National Front's candidate R Lalthangliana was leading by 590 votes in the bypoll to the Dampa assembly seat after the fourth round of counting.
The bypoll was necessitated following the death of incumbent MNF legislator Lalrintluanga Sailo in July.
Five candidates of the ruling Zoram People's Movement (ZPM), the main opposition Mizo National Front (MNF), Congress, BJP and the People's Conference (PC) party are in the fray.