A pro-Modi wave, intricate caste calculations, and lethal candidate selection may have just completed yet another BJP conquest of politically-significant Uttar Pradesh.

The mahagathbandhan, comprising big regional players Samajwadi Party and BSP, and also-ran RLD, looked strong on paper, claiming the support of major caste groups and buoyed by victories in crucial by-elections last year through near-perfect vote transfers.

A year down, major opposition leaders are facing the toughest battles on their own turf, as indicated by the exit polls. SP patriarch Mulayam Singh Yadav is on sticky wicket from his Mainpuri den, even with BSP on his side. So is daughter-in-law and former chief minister Akhilesh Yadav's wife Dimple from Kannauj.

The India Today-Axis My India exit poll shows that though Yadavs, Jatavs and Muslims in Mainpuri mostly voted for Mulayam, the BJP was able to draw all other OBCs in its favour.

WHAT IS THE CASTE ARITHMETIC?

The India Today-Axis My India exit polls gave the BJP 62-68 seats, mahagathbandhan 10-16 seats and Congress 1-2 seats.

Muslims, Yadavs and Dalits constitute around 49 per cent in Uttar Pradesh. Remove 10 per cent for non-Jatav Dalits, which makes the figure 39 per cent. This is the core constituency of the SP-BSP-RLD mahagathbandhan.

If SP and BSP votes could be transferred smoothly to mahagathbandhan candidates, the contest would have been tight. That was the expectation of opposition leaders.

GORAKHPUR, PHULPUR AND KAIRANA

But if exit polls are to be believed, the BJP has successfully replicated its formula of unifying all castes other than traditional support bases of the mahagathbandhan at the micro level.

Take the examples of Gorakhpur, Phulpur and Kairana. These three seats saw the first successful experimentation of the mahagathbandhan. Arch rivals SP and BSP had come together to defeat the BJP, albeit by slender margins, in the bypolls last year.

This time, according to our survey, the BJP is winning all three - due to a change in strategy. It has ensured that OBCs, Most Backward Castes and Upper Castes come to its side.

The BJP had successfully split the SP-Nishad Party alliance and fielded Praveen Nishad, a prominent caste leader, from Sant Kabir Nagar, adjacent to Gorakhpur. Chief Minister Yogi Adityanath had chosen Bhojpuri superstar Ravi Kishan to fight from Gorakhpur and worked hard to ensure his victory.

In Muslim-majority Kairana, the BJP won in 2014, but lost in the bypoll. This time, it has dropped its bypoll candidate Mriganka Singh and fielded Jat leader Pardeep Chaudhary.

The BJP had never won Phulpur except in 2014 when present deputy CM Keshav Prasad Maurya was the candidate. It lost the seat again in the bypoll. Here too, the BJP has changed its bypoll candidate and fielded prominent Kurmi leader Keshri Devi, with Maurya working hard to regain the seat.

DID CASTE ARITHMETIC FAIL?

Some 74 per cent Jatavs, 76 per cent Muslims and 72 per cent Yadavs voted for the mahagathbandhan - these are the core constituents of the grand alliance in UP.

On the other hand, 72 per cent non-Yadav OBCs, 74 per cent upper castes, 57 per cent non-Jatav Dalits and 55 per cent Jats voted for the BJP - this is the social coalition that the saffron party was banking on.

The answer to the exit poll results on the grand alliance's defeat lies in the seat-wise composition of castes. According to Pradip Gupta, chairman and managing director of Axis My India, if one goes seat-by-seat in the state, not all castes are present in the same proportion as statistics, which means that the mahagathbandhan's vote share doesn't add up to 39 per cent.

Going by Gupta's numbers, the mahagathbandhan did not have the caste arithmetic as strongly in its favour as was earlier predicted. Caste arithmetic did not fail. It worked, but in BJP's favour.