Bishnoi (45) lost the seat to Dushyant Chautala (26) of the INLD by a margin of 31,847 votes.
With this victory, US-educated Dushyant has also avenged his father Ajay Singh Chautala's defeat in 2009 at the hands of Bishnoi.
Bishnoi had been projected by his ally BJP as the future chief ministerial candidate of the alliance, but his defeat today may severely dent that prospect and even impact the relations between the two allies.
Dushyant is an alumnus of Lawrence School, Sanawar in Himachal and a graduate in business administration from California University in the US.
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It was a keenly watched contest in Haryana where stakes were high for Bishnoi, as he was fighting not just to retain his seat but a win or loss here was likely to have a bearing on his and his party' future.
Congress had fielded its sitting MLA Sampat Singh from Hisar, who ended at third spot.
The Hisar contest had become the most prestigious contest in the state as scions of two prominent political families-the famous 'Lals', late Bhajan Lal and late Devi Lal, were up against each other.
For Dushyant, Punjab Chief Minister Parkash Singh Badal and his Deputy, Sukhbir Singh Badal had also actively campaigned.
The HJC contested the 2009 Haryana Assembly polls independently and won six seats. However, days later five of party's legislators ditched Bishnoi and joined the Congress, which had managed to win just 40 seats in the 90-member House.
Bishnoi himself had won that year's Assembly polls from Adampur segment here.
Later in 2011, Bishnoi won the Hisar Lok Sabha by-election, following the death of his father, who was representing the Parliamentary constituency at that time.