Number Theory: Can BJP-AIADMK alliance win in Tamil Nadu?

Can a BJP-AIADMK alliance win Tamil Nadu where elections are due in 2026? Here are four charts which answer this question

The Bharatiya Janata Party (BJP) has changed its strategy in Tamil Nadu, India’s fifth most important state in terms of Lok Sabha seats. It has changed its leadership in the state and revived its alliance with the All India Anna Dravida Munnetra Kazhagam (AIADMK). What has led to a change in the BJP’s strategy in the state? Can a BJP-AIADMK alliance win Tamil Nadu where elections are due in 2026? Here are four charts which answer this question.

Union home minister Amit Shah with AIADMK general secretary Edappadi K Palaniswami, Tamil Nadu BJP president K Annamalai and others during a press conference, in Chennai, on Friday. (PTI)

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  2024 was the easiest win for the DMK alliance

  In a first-past-the-post system a party/alliance can often be rewarded/punished disproportionately. The Dravida Munnetra Kazhagam (DMK)-led alliance won all of 39 parliamentary constituencies (PCs) in Tamil Nadu in the 2024 national election with a vote share of just 46.9%. This gives a seat share to vote share ratio of 2.13, the highest a winning alliance in the state has had since 1991, the earliest year for which HT could quickly reconcile alliance-wise numbers. See Chart 1: Seat share vote share ratio of two major alliances in Tamil Nadu in all Lok Sabha elections since 1991
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  DMK’s crushing victory made the BJP’s best-ever vote share performance in Tamil Nadu completely redundant

  While the BJP could not open its account in the 2024 Lok Sabha elections in Tamil Nadu, it did manage to record its best ever performance in terms of vote share (11.3%). With a contested vote share of 19.6% -- the BJP contested 23 out of the 39 PCs – it was a party to reckon with in the state by all means. However, none of these achievements mattered given the clean sweep by the DMK and its allies. See Chart 2: BJP vote share, contested vote share and seat share in all Lok Sabha elections in Tamil Nadu
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  The 2021 elections, when the BJP was an ally of the AIADMK were a more closely contested affair

  The AIADMK surprised everybody when it won Tamil Nadu for the second consecutive time in 2016 under J. Jayalalithaa’s leadership. However, with Jayalalithaa dying within six months of the election victory, the AIADMK suffered a big blow in terms of the loss of its biggest leader , followed by a long-drawn factional fight. The 2019 elections were a rout for the AIADMK. Despite these problems, the AIADMK alliance managed to secure a significant 39.7% vote share in the 2021 assembly elections. To be sure, the DMK alliance secured a two-third majority with a 45% vote share. AIADMK’s performance in the 2024 Lok Sabha elections however was a lot worse. See Chart 3: AIADMK alliance vote share and seat share in assembly and Lok Sabha elections
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  A mechanical addition of AIADMK and BJP votes could have posed a serious challenge to the DMK alliance in 2024

  How strong will an AIADMK-BJP alliance be against the DMK led alliance in 2026 elections? If one were to add the votes of AIADMK and BJP alliance in the 2024 elections, they are higher than what the DMK alliance candidates secured in 13 out of the 39 PCs in the state. To be sure, alliances often do not see a complete transfer of votes polled by individual parties . An AIADMK-BJP alliance might or might not win the Tamil Nadu elections next year, but it will very likely challenge the incumbent. What perhaps brought the two parties together again was perhaps a realization that they would never have won the state contesting separately. See Chart 4: PC-wise vote share of DMK and ADIADMK+BJP in 2024