PATNA, India — The morning milk had yet to be delivered, but the April heat was already leaving stains on his shirt. Satyadeo Paswan’s brows furrowed as he flipped page after page of 250 caste categories, scanning for the correct code to enter in the crucial yet complicated form in front of him.

Paswan is one of the hundreds of thousands of surveyors tasked with an administratively and politically historic exercise: collecting caste data on every single one of the 126 million people in the state of Bihar.

This mammoth task has taken center stage in India’s politics. A census of caste — the rigid system of inherited social stratification sprouting from Hinduism — could transform the nation’s democratic politics. It puts the governing Hindu nationalist Bharatiya Janata Party in a tight spot: Increased caste identification could dent its electoral supremacy.

Several other states are expressing interest in conducting their own caste surveys and have sought the guidance of Bihar, according to officials here. Nearby Odisha state has begun a version, local reports say. On Thursday, however, Bihar’s high court ordered a temporary stay on releasing the results while it determines if the state government has the power to conduct the survey.

Critics of the current system say that not acknowledging and studying the role of caste in society ignores the pervasive discrimination that flows from it.

At India’s independence in 1947, the constitution outlawed “untouchability” — the most extreme form of marginalization against the lowest castes, known as Dalits. But India continued to witness caste discrimination and the maintenance of boundaries dictating who can marry whom, who can eat with whom and who can do which jobs.

The government has divided the thousands of different castes into three main categories: the Upper Castes; a middle level known as the Other Backward Castes, or OBCs; and the Scheduled Castes, or Dalits, the groups for which India’s first affirmative action programs were created, in an attempt to address their historic marginalization.

“The American society fought against racism, [but] such movements in India have been much rarer,” said Manoj Jha, a member of Parliament from the Rashtriya Janata Dal, a political party that is part of an alliance governing Bihar. “As a result, the structure is dominated by Upper Castes.”