Polling in the Radhakrishnan Nagar constituency where Jayalalithaa is pitted against CPI's C. Mahedran ended at 5 p.m. with some 65 percent of the around 250,000 electorate exercising their franchise.
The exact polling percentage would be known only when the final figures come from all the 230 polling stations, officials said.
While there are 28 candidates in the fray, only Mahendran of the Communist Party of India is viewed as a serious opponent. Jayalalithaa is widely expected to win.
There are 26 other independents and candidates from small parties including social activist K.R. Ramaswamy, popularly known as "Traffic Ramaswamy".
Polling was brisk and peaceful throughout the day since it started at 8 a.m.
Men and women voters turned out in large numbers. Schools and colleges in the constituency were closed on Saturday. The votes will be counted on June 30.
Opposition parties like the DMK, the PMK, the DMDK, the Congress, the BJP and the MDMK stayed away from the contest.
The two Left parties - CPI and CPI-M - fielded Mahendran as their joint candidate.
The Radhakrishnan Nagar constituency fell vacant after AIADMK's P. Vetrival resigned from the house to facilitate Jayalalithaa's re-election to the assembly.
Jayalalithaa, elected from Srirangam in 2011, lost that seat and the chief minister's post after a trial court in Bengaluru convicted her in the disproportionate assets case.
The Karnataka High Court upheld her appeal and acquitted her of all charges. Jayalalithaa was again sworn in as chief minister, but she has to get elected to the assembly within six months.
The Karnataka government has gone on appeal against the high court order in the Supreme Court.
The Election Commission has introduced a E-Netra system (Election Novel Electronic Tracking and Rapid Action System) in the constituency to observe the model code of conduct, monitor the expenditure by candidates, and redress complaints through a single window.
For the first time in India, the poll panel has introduced Electors Assistance System (EASY). Under this, voters in Radhakrishnan Nagar can get all election details. This facility is available through email, SMS and E-Netra MobileApp.