Polling for the Karanpur Assembly seat in Rajasthan's Sriganganagar district began at 7 am on Friday, an official said.
Surendra Pal Singh TT, the BJP nominee from the seat, has already been sworn in as a minister in the newly-formed state cabinet.
"The polling in Karanpur began at 7 am. The polling will be held till 6 pm," District Collector Anshdeep said.
Twelve candidates are in the fray. The election to the Assembly seat was deferred after the death of Congress candidate Gurmeet Singh Koonar.
The Congress has fielded Mr Koonar's son, Rupinder Singh, from the seat.
Surendra Pal Singh TT, who has been a state minister previously, was inducted into the cabinet led by Chief Minister Bhajanlal Sharma as a minister of state (independent charge) on December 30 last year, a move that was opposed by the Congress.
According to rules, non-legislators can be inducted as ministers only with the condition that they get elected within six months.
Former chief minister and senior Congress leader Ashok Gehlot called Surendra Pal Singh TT's swearing in a clear violation of the Model Code of Conduct and an attempt to influence the voters in the constituency.
The poll results will be declared on January 8, the collector said.
A total of 249 polling stations have been set up in the constituency, which has 2.4 lakh voters -- 1,25,850 men, 1,14,966 women and 10 transgender -- in addition to 180 service voters, he added.
Polling for 199 of the 200 Assembly seats in Rajasthan was held on November 25 last year.
When the results were declared on December 8, the Bharatiya Janata Party (BJP) emerged victorious winning 115 seats, beating the Congress, which could only manage to bag 69 seats.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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