Siddiqui who represented Alinagar constituency in 2015 left it and opted for Keoti assembly segment in the current state elections.
Paswan's party has, however, been instrumental in the JD(U)'s loss in at least 30 seats, as per the latest trends made public by the Election Commission.
"We are in touch with our candidates and workers from all areas and the information received from them tells that results will go in our favour," the Lalu Prasad-led party said in a tweet.
In 2010, only the CPI managed to win a seat in Bihar while in 2015, the CPI-ML (Liberation) grabbed three seats as the other two Left parties drew a blank.
As trends from all 243 seats became available, the NDA constituents were ahead in 125, with BJP candidates leading the table in 72 seats and the JD(U) in only 47.