The Shahkot bypoll was necessitated following the demise of Akali lawmaker Ajit Singh Kohar in February this year. The voting will start at 7 am and will continue till 6 pm. Votes will be counted on May 31.
The ruling Congress has fielded Hardev Singh Laddi while Akali Dal has given ticket to Mr Kohar's son Naib Singh Kohar. The AAP has fielded Rattan Singh Kakkar Kalan as its candidate.
The Election Commission has deployed over a thousand security personnel in Shahkot.
"All the necessary arrangements have been made to hold free and fair bypoll," a spokesperson of the election commission said.
There are 236 polling stations in the constituency, and webcast will be held at 103 stations. The election office has identified 136 vulnerable places.
The electronic voting machines (EVMs) and voter-verified paper audit trail (VVPAT) will be deployed at all the polling stations. Additional EVMs and VVPAT will be kept on standby to quickly replace malfunctioning machines during polling, an official said.
As the Congress desperately wants the seat in its kitty, the Akali Dal is trying hard to retain its pocket borough which made Ajit Singh Kohar its five-time lawmaker.
The main opposition AAP which faced humiliating defeat during Gurdaspur Lok Sabha bypoll and civic polls doesn't want a repeat.
The party faced embarrassment when a First Information Report or an FIR was filed against him in the case by the station house officer (SHO). However, the Congress accused the SHO of acting at the behest of SAD and AAP.
The SHO was replaced by the Election Commission over complaints of bias and violation of the code of conduct in filing of an FIR against Hardev Singh Laddi.
SAD chief Sukhbir Badal, as in charge of the poll campaign, brought three AAP leaders -- CD Singh Kamboj, HS Walia and Hans Raj Rana -- and one from the Congress -- Brij Bhupinder Singh Lalli -- into its party fold.
During campaigning, the Akalis kept up attack on the Congress on the issues like illegal sand mining, molasses leakage incident, alleged removal of Sikh history from Class 12 and "reneging" on polls promises.
Congress charged the previous Akali-BJP regime with "ruining" the state and "total lack of development" in the Shahkot Assembly constituency.
Chief Minister Amarinder Singh also criticised the Akalis for misleading farmers on loan waiver and the fiscal crisis in the state.