Bihar, with 40 Lok Sabha seats, is a crucial stop in this election for any party or alliance heading for Delhi. It was in view of this the BJP chief Amit Shah had allowed Chief Minister Nitish Kumar to have his wishlist during seat sharing, despite their shared history of ups and downs.
The 68-year-old Chief Minister, who has been ruling Bihar since 2005, had broken away from the BJP in 2013 when Narendra Modi was announced the NDA candidate for the Prime Minister's post -- a move that led to a dismal performance in the 2014 Lok Sabha elections.
Despite winning just two seats in 2014, Mr Kumar's Janata Dal United was allowed to have 17 seats -- a 50:50 division with the BJP, which had won the lion's share of 22 seats that year.
Data from previous elections hold a clue.
Mr Kumar's JDU, though small, commands a significant 15 per cent vote that can create a winner whichever way he leans.
Data shows that the BJP and Nitish Kumar, through nearly 13 years' association before the break-up, have built a huge voter base in the state -- 50 per cent compared to the 30 per cent managed by the Congress and Lalu Yadav, who are allies in this election.
The big margin ensures that the BJP-JDU combine can weather large negative swings in vote. Even a 10 per cent negative swing would give it more seats than the RJD-Congress combine. A 10 per cent swing in its favour ensures that it would scoop up 37 of the state's 40 seats.
Complementary to each other, the BJP and the JDU cover practically the entire demographics in the state -- urban, rural, men, women, upper and backward castes.
Where they face trouble is when it comes to Yadavs and Muslims -- traditional support base for Lalu Yadav and the Congress.
The woman voters are expected to make a big difference in this election. For the first time, they have crossed the number of men voters in the state.
Even all-India figures show the participation of women has equalled that of men's.
Bihar has four bellwether seats, one of which has predicted he winner in 11 Lok Sabha elections.
The last eight seats of Bihar will vote on Sunday. The counting of votes will be held on May 23.
On May 23, follow NDTV for fastest election results
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