The BJP’s win in West Bengal has evoked strong reactions across the political spectrum, ranging from celebratory acclaim to profound shock and disbelief. While the victors, led by Prime Minister Narendra Modi, have claimed this to be an anti-incumbency mandate for change, the vanquished former Chief Minister Mamata Banerjee has complained about electoral manipulations and foul play. The truth appears to lie somewhere in between.

Twin impact: SIR & Polarisation

What stood out in West Bengal’s two-phase Assembly election was the unprecedented voter turnout rate of over 93%, compared with 82% in the 2021 Assembly election and 79% in the 2024 Lok Sabha election. This 93% figure, apparently the highest ever recorded in a general election in any major Indian state, was inflated by a low base effect, as the electorate had shrunk by around 80 lakh after the Special Intensive Revision (SIR) of electoral rolls in West Bengal.

The SIR exercise commenced in West Bengal, along with 11 other states and UTs, on November 4, 2025. While it was initially scheduled to be completed by January-end 2026, a new criterion of “logical discrepancy” was introduced by the Election Commission of India (EC), only in West Bengal, to identify and remove more voters from the electoral rolls. This led to an extended process of hearings, judicial intervention, adjudication and finally an appellate tribunal process which continues till date, and is likely to continue for several years. Reportedly, over 34 lakh appeals are pending in the appellate tribunals.

En masse deletion of electors on an unprecedented scale, alongside a significant number of opaquely made additions, had a major impact on the rolls’ demographic composition. This appears to have decisively influenced the election results, besides significant anti-incumbency and communal polarisation.

While the total number of electors in West Bengal fell from 7.34 crore in 2021 to 6.81 crore in 2026, the total valid votes increased from around 6.03 crore to 6.37 crore. Total votes polled in favour of the All India Trinamool Congress (AITC) fell from 2.89 crore in 2021 to 2.60 crore in 2026—a decline of 29.5 lakh total votes. In contrast, the BJP’s total polled votes increased by 63 lakh, from 2.29 crore in 2021 to 2.92 crore in 2026. The total votes and voteshare of the CPI(M) and the Congress remained broadly the same (Table 1).

The relative magnitude of each component of the twin impact of SIR and anti-incumbency-cum-polarisation can only be understood in terms of the religious-demographic breakdown of SIR deletions. Since religio-demographic data on electors is not maintained or published by the EC, this analysis has relied on digital scrutiny of electoral rolls and deletion lists for the high-profile constituency of Bhabanipur, where BJP’s Suvendu Adhikari defeated Ms. Banerjee. Due to the absence of other reliable data from recent years, the 2011 population census has been used for the calculation of projected population of Muslims at districts and State levels.

Deletions under SIR in West Bengal occurred in three phases, viz., enumeration; claims and objections; and adjudication. Out of the 58.2 lakh total ASDD (Absent, Shifted, Deceased, Duplicate) deletions in the first phase, 32 lakh were classified as Absent or Shifted. Digital scrutiny of the ASDD lists revealed that roughly 7.34 lakh (23%) out of Absent or Shifted electors were Muslims. In the 27.16 lakh voters deleted after adjudication, which were mainly the “logical discrepancy” (LD) cases, roughly 17.65 lakh (65%) were Muslims (Table 2).

Thus, out of the total of 64.7 lakh State-wide aggregate SIR deletions, excluding deletions under Deceased and Duplicate categories, over 25 lakh were Muslims, i.e., 38.6%, which is higher than their proportion of 27% in the population as per the 2011 Census.

Statewide SIR impact analysis

An Assembly constituency-wise analysis of the impact of 67.26 lakh total SIR alterations—defined as the sum of the deletions under Absent, Shifted and LD cases and the additions during SIR—was conducted by a team of experts. Chart 1 shows the district-wise distribution of these SIR alterations, along with the district-wise shares of projected size of Muslim electors, calculated by applying the district-wise percentage of Muslim population as reported in the 2011 census. This yielded the estimated number of Muslim electors to be 1.77 crore (26%) in the total electorate of 6.81 crore.

Chart 1 clearly shows that the number of SIR alterations (deletions under three categories and additions, as explained earlier) were much higher in 12 districts with higher concentration of Muslims, namely North 24 Parganas, Kolkata, Murshidabad, South 24 Parganas, Howrah, Malda, Hoogly, Nadia, Purba Bardhaman, Paschim Bardhaman, Uttar Dinajpur and Birbhum. These 12, which accounted for over 84% of Muslim electors, also accounted for over 80% of the SIR alterations.

As six of these districts do not share any international border with Bangladesh, higher alterations under SIR cannot be easily explained in terms of suspected cross-border illegal migrants. It rather seems that the entire minority population in Muslim concentrated districts were placed under suspicion during the SIR process. This is corroborated by the findings of independent studies reported in the mainstream media, which said that at least 37% of the total deletions under SIR were Muslims.

AC-wise analysis of the results reveals that out of the 207 seats won by the BJP in 2026, the magnitude of SIR alterations exceeded the winning margin of the BJP in 82 seats. Of these, 70 were located in the 12 Muslim concentrated districts. In 2021, BJP won only 9 out of these 82 ACs. In 2026, the SIR alterations appear to have decisively influenced the electoral outcome in these 82 ACs. In other words, it is not implausible that the BJP would have failed to secure a majority in the West Bengal Assembly election without the impact of SIR.

SIR impact in Bhabanipur

This pattern of disproportionate deletion of Muslim electors possibly influencing the results is evident in Bhabanipur constituency, where digital scrutiny of polling station-wise ASDD lists and electoral rolls revealed that of the total 36,664 deletions under Absent, Shifted and LD categories, 9,481 (26%) were Muslims (Table 2). This proportion of 26% is notably higher than the 20% share of Muslims in Kolkata district’s population in 2011. These deletions of Muslim electors were highly concentrated in Parts 1 to 112 (polling booths), falling under Wards 63, 77 and 74 of the Kolkata Municipal Corporation, with high concentration of Muslim populations.

Moreover, while Muslims accounted for 26% of deletions, they accounted for only 19% (1,025) of the 5,408 additions to Bhabanipur’s electoral rolls.

AITC’s winning margin over BJP in Bhabanipur Assembly segment had already come down from 58,835 in the 2021 by-election, in which Ms. Banerjee won with a vote share of 72%, to 8,297 in the 2024 Lok Sabha election.

The net deletion of Muslim electors (total deletions excluding additions) in Bhabanipur AC during SIR was 8,456.

In the 2026 election, Bhabanipur recorded 5,524 more valid votes polled compared with the 2024, which is incidentally of a similar magnitude as the total additions during SIR at 5408.

Between 2024 and 2026, votes secured by AITC dropped by 3,649 while BJP’s votes increased by 19,753 (Table 3).

Additionally, votes polled by CPI(M) dropped by 10,540 and those by all others reduced by 1,448 between the two elections. It is likely that these votes went instead in favour of the BJP in 2026. However, such a swing in favour of the BJP is unlikely to have happened in the constituency, if not for the SIR that reconfigured the demography.

This raises fresh questions about the intent and legitimacy of SIR, which merits redressal by the Supreme Court, to prevent recurrence in other states. The inoperative and ineffectual appellate mechanism in West Bengal needs to be invigorated to ensure justice for all those wrongfully deleted through opaque, discriminatory and arbitrary processes.

The EC should be held accountable for conducting SIR in a manner that not only led to en masse disenfranchisement of genuine electors on the eve of a general election, but also endangered the future of free and fair elections in the country, which is the cornerstone of parliamentary democracy. The EC must publish a comprehensive statistical report of all SIR related data on deletions, additions and modifications to the electoral rolls in West Bengal, which are hitherto not officially reported, to facilitate further independent analysis and judicial scrutiny.

Prasenjit Bose is an economist. He heads the SIR Committee of the West Bengal Pradesh Congress Committee