On the banks of the Ganges river, in one of the holiest cities for Hindus, a former physics professor is battling a murder suspect to unseat a first-time member of parliament.

The political battle for Varanasi is one of the most closely watched in the first round of voting in India’s parliamentary election, which started on Thursday as millions flocked to the polls in the world’s largest democracy to begin the month-long process of choosing a new government.