Neither of the two main national parties -- the incumbent Congress and the Hindu nationalist Bharatiya Janata Party (BJP) -- is seen as capable of securing an absolute majority in the five-stage polls beginning Thursday.
With a myriad other parties expected to grab up to 50 percent of the 543 parliamentary seats on offer, the final result will kick off an intense period of political horse-trading as the big players rush to form a working coalition.
"At the moment, Congress seems to have the advantage as more parties appear willing to do business with it," said Mahesh Rangarajan, a professor at Delhi University.
"But if the Congress party falls short of 135 seats on its own, then finding partners will be difficult.
I wouldn't say it's wide open but it's certainly an open situation.
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Thursday's first phase of voting will take in large swathes of northern and eastern India, including areas beset by a range of violent insurgencies involving tribal rebels, Maoist guerrillas and Muslim