Prime Minister Narendra Modi's chances of getting re-elected in the 2019 elections have slipped from 99 per cent in 2017 to 50 per cent, says economic analyst Ruchir Sharma, noting that a fragmented opposition is showing signs of coming together.

The BJP won with 31 per cent vote share in 2014 because the opposition was fragmented, seat share was disproportionate and its vote was concentrated, said the New York based columnist and economist who is working on his new book Democracy on Road.

The 2019 elections are going to be a complete toss up. If I was a betting person, this time last year I would say chances of Modi getting re-elected were 99 to 1, which basically means it was a done deal yes, it appeared that way after the UP election wave.

However, the odds have shifted dramatically. Now it is a 50:50 election and a lot is going to come down to alliances again. The opposition, from being totally fragmented, is now actually showing signs of coming together that's India for you, nobody likes if it becomes one-sided, Sharma told PTI in an exclusive interview.

The economist has a keen eye on world politics, especially India. His new book, which is expected to hit the stands in February ahead of the 2019 elections, claims to provide an insightful account of how Indian democracy works, using elections as a lens.

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Sharma, who has covered two dozen elections in India since 1990s, recalls the 2004 elections and argues that the gap in popularity between then prime minister, the late Atal Bihari Vajpayee, and the opposition is similar to the situation between Modi and the present opposition today.

You (BJP) won with 31 per cent vote share because the opposition was fragmented, seat share was disproportionate and the BJP's vote was concentrated.

And even against Vajpayee, when the opposition began to come together, the same question was asked, who will become the PM, if not Vajpayee' and you had an accidental PM, said Sharma who earlier wrote the New York Times bestseller The Rise and Fall of Nations".

In 2004, the BJP-led National Democratic Alliance (NDA) conceded defeat and the Congress returned to power with Manmohan Singh being appointed prime minister.

Describing Uttar Pradesh, which has 80 Lok Sabha seats, as a microcosm of India, Sharma said if there is an alliance between the Bahujan Samaj Party and the Samajwadi Party in the state, they will sweep the elections. Otherwise, it will be the BJP, as simple as that.

According to Sharma, the vote in Uttar Pradesh is still decided on the basis of caste.

... it is just about how the caste and arithmetic are going to work depending on the alliance in that way, nothing has changed there in past 30 years. Because the question Who are you going to vote' in UP is still along caste lines, if you are an upper caste you will vote BJP, Dalit then Mayawati everybody there laughed when I asked them about development being an issue, he said.

Of 26 election trips that he has taken across the country, six or seven have been in Uttar Pradesh, he said.

Bijnor, a small town in the state, where he spent some of his childhood will make the first and concluding chapter of "Democracy on Road".

This is how I try to go the whole circle in the book, Sharma said, adding that he plans to do one more election trip for the book during the upcoming state election in Rajasthan and Madhya Pradesh.

To be published by Penguin Random House India, the book is touted to be a must read before the 2019 elections.