Can Modi finally win over the southern states and reshape India’s electoral map?

K Annamalai, one of the BJP’s most talked-about candidates, is campaigning in Tamil Nadu, where Modi hopes to make major gains Photograph: Jagadeesh Nv/EPA

Under Tamil Nadu’s scorching midday sun, K Annamalai waved at the crowd gathered around his campaign bus. Some people stretched their babies upwards to be touched by him, others threw flower petals and passed gifts through the window. A sea of mobile phones vied for space as people tried to squeeze the candidate into their selfies.

Here in Coimbatore, an industrial city in the southern state of Tamil Nadu, Narendra Modi’s Bharatiya Janata party (BJP) has been working overtime. Over months, thousands of volunteers and party workers have taken to the streets – backed hundreds of locally-targeted WhatsApp groups and a highly-organised social media campaign across YouTube, Facebook and Instagram – whipping up a frenzy around Annamalai, one of the BJP’s most talked-about candidates.