India, Aug. 22 -- Under big yellow block lettering, a group of men lumber around a shed next to a blue ice cream freezer and orange campaign posters bearing the lotus emblem. Behind them is the exposed engine of a lorry, framed by half-raised yellow shutters and contact numbers. Raw concrete pillars and scaffolding support an unplastered second storey. Below, broad bands of saffron, white, and green cover the ground floor. Small saffron flags hang from the railing, echoing the lotus motif.

Off Diamond Harbour Road near the southernmost tip of Bengal, the venue for the gathering one scorching July morning might be humble, but the purpose is anything but. Around 200 people, mandal and block-level spokespersons and leaders of the Bharatiya ...