The 57 seats, including 24 in the Seemanchal region bordering West Bengal, are spread over nine districts of Madhubani, Darbhanga, Supual, Madhepura, Saharsa, Araria, Kisanganj, Purnea and Katihar.
Prime Minister Narendra Modi led the charge on behalf of the NDA, which has not declared a chief ministerial candidate, and launched a blistering attack on the JD(U)-RJD-Congress grand alliance.
Modi, who addressed around 30 election rallies, unusual for a Prime Minister in a state poll, repeatedly referred to alleged attempts being made by the grand alliance to "snatch away" a part of the quotas meant for dalits, tribals and backward classes and give it to a "particular community on the basis of religion".
Chief Minister Nitish Kumar and RJD boss led the counter attack against Modi and BJP chief Amit Shah, who said in a controversial statement that celebratory firecrackers will be burst in Pakistan if BJP lost Bihar.
Hitting back, Kumar said Mumbai and Amritsar will witness "maximum fireworks" if BJP lost, apparently referring to strained relations of the party with its allies in Maharashtra and Punjab.
Kumar also sought to turn tables on Modi, who scoffed at his meeting with an occultist, as he targeted the Prime Minister, rally after election rally, for allegedly consulting astrologer Bejan Daruwala.
