The vote would be held in six districts - Gopalganj, Siwan, Vaishali, Saran, East and West Champaran and Rabri Devi has been in the fray from Raghopur and Sonepur assembly seats.
According the experts, the third phase, unlike the previous two phases, would be a test for Chief Minister, Nitish Kumar's claims of good governance and rule of law as well as his development plank.
The ruling National Democratic Alliance (NDA) of Nitish Kumar's Janata Dal-United (JD-U) and the Bharatiya Janata Party (BJP) currently holds 27 of the 48 seats.
The RJD-LJP holds 14 seats, Congress 1, Bahujan Samaj Party 1, the Communist Party of India-Marxist Leninist (CPI-ML) 1 and Independents 4 in the belts.
After the third phase, the next rounds of elections would be held on Nov 1, 9 and 20. Votes would be counted on Nov 24.