While Kushwaha will contest from Karakat, Kumar will be in the field from his native Jehanabad constituency.
The party, which has been alloted three seats out of 40 in Bihar is yet to finalise the candidate for the third seat Sitamarhi.
"We will finalise the candidate for Sitamarhi in 3-4 days," Kushwaha told reporters here.
Asked if the three seats alloted to it were as per their choice, the RLSP chief, who is a native of Vaishali district and will contest Karakat seat for the first time, answered in affirmative.
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While Karakat is in south-central part of Bihar, Jehanabad is in central Bihar and Sitarhi in Northern part of the state.
The RLSP chief, a former close supporter of Chief Minister Nitish Kumar but who later fell out with him to float a new party, exuded confidence that NDA would perform exceedingly well in the state to fullfill the mission of making Narendra Modi as Prime Minister of the country.
He said Modi who hails from extremely backward caste would realise the dream of Jannayak Karpoori Thakur by becoming the prime minister of India but Nitish Kumar is trying to "betray" this dream of Thakur by not supporting him.
"Our tie up with BJP is not for one election...After winning Parliamentary elections we will like to win Bihar Assembly polls next year to oust Nitish Kumar from the power," he said.
The party received a boost with the joining of state Congress General Secretary Shambhu Nath Sinha.