While the NDA's candidate is highlighting the development works done by Chief Minister Nitish Kumar, the RJD candidate, who is hoping to draw the Extremely Backward Class (EBC) votes to its traditional Muslim-Yadav electoral bank, is relying on Mr. Kumar's "betrayal" of the Grand Alliance, making it his selling point of the campaign.
By 12 noon, 31.25 percent voter turnout was recorded in Bihar's Araria constituency, 24.5 percent in Bhabhua and 28.6 percent in Jahanabad.
By-elections are being held in Gorakhpur formerly held by Chief Minister Yogi Adityanath - and Phulpur Lok Sabha seats in Uttar Pradesh.
According to election commission sources, the polling is so far peaceful.
In Bihar, voting is being held for bypolls to the Araria parliamentary seat.
A poll official in UP said there were complaints of electronic voting machine malfunctioning at a few booths, but the EVMs were promptly replaced without affecting the polling.More news: Elizabeth Warren not running for president
The Bihar bypolls have a special attention as Janata Dal-United (JDU) and chief minister Nitish Kumar has joined hands with the arc rivals Bharatiya Janata Party (BJP) and contesting against old partners RJD-Congress.
JD (U) had initially stated that it will not contest the bye-elections but later relented at BJP's urging to contest from Jehanabad.
From Bhabua Assembly seat in Bihar, the BJP has fielded Rinki Pandey, widow of sitting BJP MLA Anand Bhusan Pandey, whose death necessitated the bypolls.
The Araria lok-sabha bypoll was necessitated by the death of RJD MP Mohammed Taslimuddin.
This is the first electoral battle in the state since Chief Minister Nitish Kumar, who also heads the JD (U), walked out of the alliance with the RJD and the Congress and joined the BJP-led NDA a year ago. "Fresh polling must take place in all these booths", said Quadri. The saffron party has fielded Pandey's wife Rinky Rani and her principal challenger is Congress candidate Shambhu Singh Patel.
A total of ten candidates are in the fray from Gorakhpur, while 22 candidates are in the arena from Phulpur.