Mr Dhillon was a member of the Punjab Legislative Assembly (2012-17) for the constituency of Barnala.
The Bharatiya Janata Party on Monday fielded former Congress leader Kewal Singh Dhillon as its candidate for Lok Sabha by-elections in Punjab's Sangrur.
AAP has fielded Gurmail Singh from the seat.
The seat fell vacant after Bhagwant Mann won the assembly election from the Dhuri constituency in the Sangrur district.
In the recently concluded Punjab Assembly elections, Mr Dhillon contested as a Congress candidate against AAP's Bhagwant Mann. He had secured 3,03,350 votes.
A loyalist of former Punjab Chief Minister Captain Amarinder Singh, Mr Dhillon was a member of the Punjab Legislative Assembly (2012-17) for the constituency of Barnala.
Notably, Mr Dhillon was among the eight leaders the security cover of whom was revoked by the Aam Admi Party government on May 11, citing "no specific threat".
Mr Dhillon joined the BJP on June 4 with six others.
Apart from Mr Dhillon, former ministers Raj Kumar Verka, Balbir Singh Sidhu, Gurpreet Singh Kangar, and Sundar Sham Arora were among the seven Congress leaders who joined the BJP on June 4. Congress leader Kamaljeet S Dhillon and the sitting Mayor of Congress in Mohali, Amarjeet S Sidhu also joined the BJP then.
Today is the last day for the candidates to file nominations for the bye-election. The filing of nominations began on May 30, the scrutiny of nominations would be done on June 7 and the last date of withdrawal of candidature is June 9. The polling will take place on June 26.
The Aam Aadmi Party (AAP) registered a landslide victory in the Punjab polls with 92 seats, pushing most of its rivals to the margins. Congress won 18 seats in the 117-member Assembly.
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