At least 117 Lok Sabha seats most likely to be impacted by vote swings may ultimately decide the fate of NDA in the upcoming general elections. These seats are spread over several states, including Uttar Pradesh, Karnataka and Jharkhand, where new alliances of opposition parties are posing a threat to the BJP-led alliance.

According to an analysis of the data collected by Credit Suisse - a multinational investment bank and financial services company - of these 117 seats, Bharatiya Janata Party (BJP) had won 73 in 2014 with a margin less than 10 per cent.

Of the remaining 44 seats, BJP had won 34 in Uttar Pradesh with more than 10 per cent margin but these are also likely to be impacted because of the alliance between the two principal opposition parties - Samajwadi Party (SP) and Bahujan Samaj Party (BSP). The balance 10 seats are in Karnataka and Jharkhand, where Congress has forged alliances with regional parties.

LOW MARGINS AND NEW ALLIANCES

The Credit Suisse analysis states that in almost all elections prior to 2014, nearly 300 of the 543 seats had a victory margin of less than 10 per cent. But in 2014, which political analysts called a "wave election", this dropped to less than 200 seats. There was an across-the-board improvement in the BJP's vote share in the northern, western and eastern states. As many as 161 of the 543 Lok Sabha seats had victory margins in excess of 20 per cent (BJP winning 117 of these) and only 98 seats had margins less than 5 per cent (BJP winning 30 of these).

Critical for the BJP are the 73 seats it had won by less than a 10 per cent margin, which are under threat of the changing alliances as well as 130 million new voters.

In addition, the new SP-BSP alliance threatens another 34 seats in Uttar Pradesh because of the possibility of a perfect transfer of votes. This arithmetic would be more complex in Jharkhand and Karnataka where it may be harder to predict vote transfer as vote banks are less firm than for the SP and BSP in Uttar Pradesh. In Karnataka for instance, Congress and JD(S) dominate different geographical regions and the alliance may itself not consolidate votes.

FRAGMENTATION OF VOTES

The Credit Suisse analysis also shows that the average victor has garnered a vote share of 45-48 per cent in the past three decades. The average gap between the winner and the runner-up, however, has stayed in the range of 10-14 per cent of votes cast since 1991, though it went up to 15 per cent in 2014.

The analysis shows that fragmentation of votes was less in 2014 compared to most states in 2009, but it worsened in states like West Bengal, Tamil Nadu and Kerala where the BJP or its allies made inroads, though not large enough to win seats.

The alliances of opposition parties in Uttar Pradesh, Jharkhand and Karnataka, however, are likely to reduce fragmentation of votes and work against the BJP.

WILL FIRST-TIME VOTERS HAVE AN IMPACT?

New voters are a critical factor behind vote swings. About 130 million new voters (16 per cent of the 2014 vote base) are likely to be registered for the upcoming elections and their preferences are unknown. Political strategists believe that a turnout of these voters is usually much lower than the average turnout, either because they don't bother to get their names added to the voters' list, or a general apathy towards government and governance.

While in 2014, there was a sharp increase in the turnout of new voters (more than 66 per cent), it may not be the case in 2019. Though a high turnout in recent state elections suggest that it may not fall off sharply.

Disclaimer: These calculations may change if new alliances are formed in Tamil Nadu where the BJP and AIADMK are in talks, or in Assam and Jammu & Kashmir where possibilities for alliances still remain.

(This report is based on the analysis of electoral data provided by Credit Suisse)