Tens of millions of Indians are heading to the polls in the first phase of the biggest general election in the world.Lengthy queues are expected to begin forming on Thursday morning for the opening round of voting in 91 constituencies across 20 states and regions.The election is divided into seven phases to help manage the sheer number of people who could end up having their say on who should fill the 543 parliamentary seats, with some 900 million eligible to vote.It means it will not come to an end until 19 May, with the results to come four days later on 23 May.The ruling Hindu nationalist Bharatiya Janata Party (BJP) has been tipped to come out on top in an election that will see heightened security.Seven people were killed in militant attacks in Kashmir and the east of the country on Tuesday.Prime Minister Narendra Modi has been riding high over his tough stance against Pakistan since aerial clashes between the neighbours in February.While the main opposition Congress party has garnered support by criticising the government for high unemployment, and wrested three major farming states from the BJP in December, it is still expected to fall short.An average of four opinion polls have the BJP winning a majority of 273, despite official government statistics showing that Mr Modi's administration had failed to create enough jobs for a population of 1.3 billion.Image:It is expected that Narendra Modi will be hard to beatShould the prediction come to pass, the BJP would be significantly down from the 282 seats secured in 2014 - the first clear majority in decades.According to Gilles Verniers, a political science professor at Ashoka University near New Delhi, the problem for those who want a change is that the opposing vote is split.Image:Rahul Gandhi leads the main opposition Congress partyHe explained: "The gap between Congress and the BJP is still enormous, so no one is seriously thinking that Congress is going to fill that gap"The opposition landscape remains heavily fragmented."Congress only won 44 seats last time around, and is now pinning its hopes on a promise of monthly handouts of 6,000 rupees (£66.28) for the poorest families to boost its performance.Image:There will be tight security at the polling stations during the first phase of the electionOne seat it is all but guaranteed to hold on to is that of party chief Rahul Gandhi, from the most famous political dynasty in modern Indian history.He has filed nomination papers in the family stronghold of Amethi in Uttar Pradesh state, hoping to secure a key seat for the fourth general election in a row.More than 142 million Indians are eligible to vote on Thursday, with the second phase scheduled for 18 April.