Anything can happen in this election.
BJP may still form a government with the outside support of some regional parties with Modi as the PM but then, he will be like a bird with clipped wings - facing difficulties every day with pulls and pushes of the regional shatraps.
The other option could be that BJP forms a government in alliance with other parties who may join NDA if BJP is ready to form a govt with another leader in place of Modi.
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Yes. During the election under "India Shining" Slogan, under Bajpayee, the outcome was surprising. Secondly, Kejriwal can be " bone of contention". As the famous adage goes "there is still a slip between the Cup & the Lip". Modi should go like hands-in-gloves with people of all communities, hence.