Indian politics – since the split in the Congress Party ranks under Indira Gandhi in the late 1960s – has become an increasingly regional affair in which the two main national parties – Congress and the Hindu nationalist Bharatiya Janata Party – can only win power by striking alliances with local state-based parties.
For Narendra Modi to become prime minister, the National Democratic Alliance (NDA) that his party leads must cobble together 272 seats in the Lok Sabha parliament.
Recent opinion polls suggest its members – which include the Punjab-based Sikh party, the Shiromani Akali Dal, the Tamil Nadu-based MDMK and the Bihar-focused Lok Janshakti Party of Dalit leader Ram Vilas Paswan – may win more than 200 seats.
CNN-IBN poll tracker suggested it could win as many as 246, with the BJP itself winning 218.
If the poll is near accurate, the BJP's NDA would be expected to attract opportunist parties – there are many – and independents to its ranks with the prospect of power. In this scenario, Modi would be in an unassailable position to become India's next prime minister.
Many suspect however – and the Congress leadership desperately hopes – that recent fissures starting to appear within the BJP's ranks indicate a more troubled campaign than expected and that the NDA may not win nearly so many seats.
Amar Singh, a member of the Rajya Sabha upper house and a former Samajwadi Party leader who is now a Congress ally, said he believes the NDA may be the largest solid group but may not win more than 150 seats.
"Senior leaders, including Sushma Swaraj and LK Advani have been unhappy. This has lowered the moral ground of Modi's attack on the Congress. I don't think the NDA will get more than 150 seats and that will be a 100 per cent disaster for Modi," he said.
In this scenario, he said, the non-Congress, non-BJP parties – the so-called Third Front of regional parties including the Samajwadi Party, Communist Party of India (Marxist), Janata Dal (United), and the AIADMK which rules in Tamil Nadu – could form a group with other secular, regional parties to form a winning alliance with the Congress Party's United Progressive Alliance (UPA).
One senior Janata Dal (United) source said although no one would openly discuss this scenario ahead of the election, it would consider an alliance, which included Congress, to stop Narendra Modi becoming prime minister.
"If the BJP and NDA get under 200 seats it will be difficult for them to form a government because it is difficult under Modi for others to ally with them – all of the possible allies have people of many faiths in their own areas of influence. Modi is anathema to Muslims," he said.
Many of his potential allies, like Mamata Bannerjee's Trinamool Congress, which rules in West Bengal, Mayawati's Bahujan Samaj Party in Uttar Pradesh, and Jayalalithaa's AIADMK, which rules Tamil Nadu, all need Muslim votes, he explained.
His party, whose leader Nitish Kumar is chief minister in Bihar, hopes his Third Front will eventually draw Congress into supporting it as a minor group.
Shaheed Siddiqui, a former MP from Uttar Pradesh and a leading Muslim voice in India said he doubted whether the regional parties necessary to form a Third Front government could overcome their local rivalries.
The coveted PM's post can also be a blockade in that goal, he added.
These bitter local and personal rivalries mean the Congress, even greatly diminished, could still emerge as the only party their fractious allies may agree on to lead it in government.
"I don't think any of these individual parties will win more than 40 seats and it will be difficult for them to accept anyone else as leader. Congress will still be the largest of them," he said.