Impossible job: India's pollsters face the uphill battle to call election

Current surveys could be wide of the mark until the parties finalize alliances, which could be as late as April - and even then, there are challenges.

Thousands of candidates, hundreds of parties, endless combinations of possible coalitions – spare a thought for India’s pollsters, tasked with making sense of the country’s fiendishly complicated politics ahead of a general election due by May. 

The ruling Bharatiya Janata Party led by Prime Minister Narendra Modi won a surprise majority in 2014. Until last year, many predicted a similar result. But amid rising anger over unemployment and a fall in rural incomes, the BJP lost key state elections in December, making this contest more closely fought than first expected.

That means surveys conducted on behalf of newspapers and TV channels will