Polling in the Yercaud assembly constituency in Tamil Nadu to decide the fate of 11 candidates began Wednesday morning.
The fight will be mainly between the ruling AIADMK's P. Saroja and DMK's V. Maran. All others are independents.
Around 2,500 police personnel have been deployed in the constituency.
The by-election in the hill station, around 360 km from here, was necessitated after AIADMK legislator C. Perumal died in July. Saroja is Perumal's wife.
