Polling was underway on Monday for the by-election in the Maoist-hit Lohardaga assembly constituency in Jharkhand amid tight security.
More than 20 percent of voting, which began at 7 a.m.., had been reported at 11 a.m. There are nine candidates in the fray whose fate will be decided by 2.20 lakh voters at 272 polling stations.
The three main candidates are Niru Bhagat of the All Jharkhand Students Union (AJSU), who is supported by the ruling BJP, Sukhdeo Bhagat of the Congress and Bandhu Tirkey of Jharkhand Vikas Morcha-Prajatantrik (JVM-P).
The Lohardaga seat fell vacant after the incumbent, AJSU legislator Kamla Kishore Bhagat, was convicted and handed a seven-year jail term in July in an extortion case.
Niru Bhagat is the wife of Kamala Kishore Bhagat.
The bypoll is being regarded as a litmus test for the ruling BJP. The seat is reserved for tribals.
Jharkhand currently has its first non-tribal chief minister in office.