Members of Votadhikar Raksha Mancha stage a protest demanding voting rights for deleted voters ahead of the West Bengal Assembly elections in Kolkata

The Special Intensive Revision (SIR) of electoral rolls in West Bengal, announced on October 27, 2025, by the Election Commission of India, has emerged as a decisive factor in the 2026 Assembly elections, particularly in constituencies where victory margins were under 10,000 votes. Election results suggest that in tightly contested seats, the scale of voter deletions and adjustments often exceeded the eventual winning margins, amplifying its electoral impact. The SIR process, marked by procedural disruptions, led to the deletion of around 91 lakh electors and placed another 27 lakh under adjudication, with appellate tribunals constituted following directions of the Supreme Court.

An analysis by businessline of constituencies with narrow margins shows that the SIR’s imprint is most visible where contests were closest. In the absence of the exact number of deletions under the SIR for each constituency, we took a proxy measurement, by subtracting the number of eligible voters in these constituencies as published by the ECI on the last date of filling nominations from the number of eligible voters as published by the ECI in 2024. The data reveals a consistent pattern: in a majority of these seats, the reduction in voters was larger than the margin of victory, indicating a direct bearing on outcomes.

Victory margin

Among the 21 constituencies where the victory margin in 2026 was under 5,000 votes, 20 was won by the AITC in 2021, most with margins exceeding 10,000. Only one constituency was won by the BJP in 2021. By 2026, however, 12 of these had switched to the BJP and one to Congress, leaving AITC with just 7 seats and that too with sharply reduced margins.

Take Indus, the lone seat in this category that the BJP had held in 2021. The constituency saw a relatively modest reduction of about 4,000 electors, far lower than others in this group, and the party managed to retain it, though its margin shrank dramatically from around 7,000 in 2021 to just 900 in 2026.

Contrast this with Haripal, where the drop in eligible voters was roughly 10,000. AITC had won here comfortably in 2021 by about 23,000 votes; in 2026, the seat flipped to the BJP with a narrow margin of 3,500.

The most striking cases are Kashipur-Belgachia and Rajarhat-New Town, both in the greater Kolkata metropolitan region. Kashipur-Belgachia saw a reduction of nearly 53,500 electors, far exceeding any victory margin, turning a 35,400-vote AITC lead in 2021 into a 1,600-vote BJP win in 2026. Rajarhat-New Town exhibited a similar pattern, underscoring how large-scale revisions in urban constituencies translated into electoral reversals.

Victory margin

The pattern persists in the next band of 28 constituencies, where victory margins ranged between 5,000 and 10,000 votes. Here, too, SIR-induced changes appear to have played a decisive role in shaping outcomes.

A high-profile case is Nandigram, long associated with BJP strongman Suvendu Adhikari. BJP had won the seat in 2021 with a slender margin of about 2,000 votes. Notably, Nandigram saw one of the lowest reductions in voters at around 7,000, and in 2026, the BJP not only retained the seat but expanded its margin to roughly 9,000 votes, suggesting limited disruption relative to other constituencies.

Similarly, Darjeeling, another BJP-held seat in 2021 with a margin of 21,000, witnessed a reduction of about 39,000 electors. This sharply compressed the BJP’s victory margin to 6,000 in 2026, highlighting how even incumbents were affected where deletions were large.

In contrast, Patashpur, located near Nandigram, recorded the smallest reduction in voters, just about 1,000, among all 49 constituencies analysed. AITC had won this seat in 2021 with close to 10,000 votes, but in 2026, it flipped to the BJP, which secured it with a margin of 9,000. The minimal change in voter rolls here suggests that factors beyond SIR also played a role even as the broader trend points to its significance.

Across this category, barring exceptions like Patashpur and Nandigram, most constituencies saw reductions far exceeding the eventual victory margins, reinforcing the disproportionate influence of the roll revision. Of the 26 seats held by the AITC in 2021, 16 switched to the BJP in 2026, one went to Congress and the AITC retained 9, mostly with diminished margins. Only in Nanur did the AITC manage to increase its margin of victory compared to 2021.

Broader takeaway

Taken together, across the 49 constituencies where victory margins were under 10,000 votes, a total of 28 seats shifted from the AITC to BJP between 2021 and 2026. The data suggest that in these closely fought contests, the SIR did not merely update electoral rolls, it reshaped the competitive landscape, with even marginal changes in voter numbers proving sufficient to overturn previously comfortable leads.

Published on May 8, 2026