Though there are a total of 28 candidates in the fray but the battle is effectively between Jayalalithaa and CPI's C Mahendran, addressed by his comrades as 'CM'.
This has prompted the Left parties to dub the electoral battle as a 'CM vs CM fight.' CPM is also backing Mahendran.
Counting of votes will be taken up on June 30.
However, Jayalalithaa on her part addressed only 2 meetings during the bypoll campaign as she assured implementation of her election promises.
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She chose to address the meetings in her personal vehicle that had a microphone fitted in it.
The AIADMK supremo, during the campaign, refrained from any vitriolic attack against the opposition, including arch rival DMK, and chose to highlight her four year-old government's achievements in various sectors.
She claimed that main opposition parties had stayed away from contesting as her party could not be defeated.
The bypoll has been necessitated to this North Chennai constituency after AIADMK's P Vetrivel had vacated it in May, apparently to enable Jayalalithaa seek re-election.
The AIADMK supremo has to fulfil a constitutional requirement of getting elected as MLA within six months of becoming Chief Minister.
Jayalalithaa returned to the top post on May 23 after securing an acquittal in a wealth case. She had been convicted in the case in September last by a trial court in Bangalore.
Social activist 'Traffic' Ramasamy is among the 26 independent candidates trying his electoral luck.
The EC has also issued a list of regulations post the end of campaigning period that includes barring public meetings and asking outsiders to leave the constituency.
EC has prohibited releasing results of opinion polls and exit polls.