Following a postal strike, only 12 postal votes was counted out of some 900 ballots.
A total of 76.25 per cent of the electorate in the constituency voted besides 228 NRI voters.
The by-polls for the Chengannur Assembly seat was necessitated following the death of CPI-M legislator K.K. Ramachandran Nair in January.
While the CPI-M decided to field district party secretary of Alappuzha, Saji Cherian, the Congress has brought in D. Vijayakumar, a party veteran from Chengannur.
BJP sought its former state Party president P.S. Sreedharan Pillai to contest the by-polls.