There are many reasons why BJP has swept Uttar Pradesh. There is the popularity of prime minister Narendra Modi, the management of president Amit Shah, the anti-incumbency against the Samajwadi Party, there is Hindutva and the division of Muslim votes, there's the positive ratings for demonetisation. But the most important reason why the BJP has won UP is caste.
It was the BJP's re-capture of non-Yadav OBCs that led it to sweep UP in the Lok Sabha elections in Uttar Pradesh, and the caste arithmetic continues. The arithmetic is simple and unbeatable. Since 2014, the BJP has chosen to target everybody except Yadavs, Jatavs and Muslims. The rest is 60% of the population. Non-Yadav OBCs together with upper castes are at least 50% of the population.
Non-Yadav OBCs were first brought into the BJP fold in the 1990s. Their association with the party, therefore, goes back a long time. It was the split in the upper caste plus non-Yadav OBC combine that led to the party's decline in UP. Putting together the caste coalition again has brought the BJP back in the game.
Singularly the most important aspect of this strategy was getting Kalyan Singh back in the party in March 2014. The Lodh leader brought back Lodh votes in the party. In the seats of his influence in lower west UP, his breakaway party used to get more votes than BJP candidates, With his re-entry, the Lodh plus upper caste combination has again become indomitable. Just the arithmetic is so strong, it is difficult for it not to win most seats of Lodh influence.
Or take the case of Kurmi voters in east UP. The BJP did an alliance with the Anupriya Patel faction of Apna Dal, a Kurmi party. Like it made Kalyan Singh governor of Rajasthan, it made Anupriya Patel a central minister. Apna Dal (Soneylal) contested 12 seats, has won 6 at the time of writing, and is leading in another three.
Rajbhars here and Nishads there, Kushwahas and Mauryas--all kinds of small and big non-Yadav OBC communities were co-opted by the BJP. This was their central strategy. It worked on them, giving them tickets and leadership in the party, the most important aspect of which was making a Maurya their local face. It helped that Keshav Prasad Maurya belonged to this section of society, just as Narendra Modi's own caste, Teli, helps non-Yadav OBCs identify with them.
This is also what explains why the BJP went for not just anti-Muslim but anti-Yadav polarization, accusing the Samajwadi Party of discrimination in governance on account of religion and caste. BJP workers on the ground focused on the anti-Yadav resentment amongst these communities.
Many of these communities became allied to the Bahujan Samaj Party and the Samajwadi Party as the BJP declined. Their return to the BJP is so consolidated that it's hard to find a non-Yadav OBC who's not a Modi fan. Upper castes also speak of Modi, but they are traditional BJP voters who said they were voting BJP or its lotus symbol. Non-Yadav OBCs said "Modi" even though it was a state election.
They spoke of Modi with faith and respect, even if they couldn't always articulate why they were enamoured of him. They'd say demonetisation showed Modi was serious about fighting black money, or mention the strike in Pakistan, Jan Dhan or Ujjwala gas connections. Yet it wasn't about any of these. As one voter said, "I like Modi. I like to listen to him. I feel good when I hear him speak. Whether he says the right thing or wrong." They support demonetisation, but that's not what made them Modi's fans.
Yes there is Hindutva, but the BJP has benefited less from polarisation and more from the split of Muslim votes. The Congress alliance gave the impression that SP-Congress would get a bulk of Yadav and Muslim votes, further alienating any non-Yadav OBCs or upper castes who were thinking of voting SP for the sake of Akhilesh Yadav.
None of this is to take away from Modi's popularity or Amit Shah's strategies. It's not one or the other, it's a combination of factors. The most important of these was caste.
Also in HuffPost: