INDIA’S general election will take place before May. The front-runner to be the next prime minister is Narendra Modi of the Bharatiya Janata Party, currently chief minister of Gujarat. A former tea-seller, he has previously attacked leaders of the ruling Congress party as elitist, corrupt and out of touch. Now he is emphasising his humble caste origins. In a speech in January he said “high caste” Congress leaders were scared of taking on a rival from “a backward caste”. If Mr Modi does win, he would be the first prime minister drawn from the “other backward classes”, or OBC, group. He is not the only politician to see electoral advantage in bringing up the subject: caste still matters enormously to most Indians.

The country’s great, liberal constitution was supposed to end the millennia-old obsession with the idea that your place in life, including your occupation, is set…