Secular Democratic Alliance^[6][7] (Bengali: ধর্মনিরপেক্ষ গণতান্ত্রিক জোট) is a political alliance formed ahead of the 2024 Indian general election in West Bengal by the Communist Party of India (Marxist) and the Indian National Congress in opposition to the Trinamool Congress and the Bharatiya Janata Party.^[8][9][10]

Following the heavy defeats in the 2011 Legislative Assembly election and the 2014 general election, the CPI(M) welcomed ideas of the alliance even with non-communist parties. The first signs came when in the Siliguri municipal election, CPI(M) made some local understanding with INC resulting in CPI(M) leader Ashok Bhattacharya being appointed as the mayor. This success got popularity as "Siliguri Model".^[11] After the success of the model, in the long run, some Congress and CPI(M) leader advocated for a Left-Congress alliance.^[12] This gradually materialized into "alliance" between INC and Left Front in all the seats except in Murshidabad district.

Given the political history of West Bengal, the materialisation of an alliance between the Congress & the CPI(M), 2 parties that have been bitter rivals of each other since the 1970s & have a history of unleashing political violence against each other's cadres, took the political circles of the state by surprise. After much dispute and secession of SUCI(C) and CPI(ML)L from the Left Front, both Congress and Communists formed an understanding basis of what they called "seat-sharing", strongly objecting to the use of the word "alliance".

In 2016, Mahajot^[13][14] was formed on the broad agreement that some political parties proposed before the 2016 West Bengal Legislative Assembly election for fighting against the Trinamool Congress government in West Bengal and the Bharatiya Janata Party on national level. Left Front consisting of CPI(M), CPI, RSP, AIFB and DSP along with INC released their respective candidate list in several rounds after consultations and bargaining.^[15][16] However, the alliance failed to gain the majority seats in the assembly elections.^[17] Afterwards, ahead of 2019 Indian general election, the alliance between the Congress and the Left Front is off the cards as both camps could not agree on a seat-sharing formula for Lok Sabha elections.^[18][19]

Subsequently, Mahajot succeeded to Sanjukta Morcha^[20] in 2021 with the joining of ISF in the alliance. After the 2021 West Bengal Legislative Assembly election, Adhir Ranjan Chowdhury, the head of Congress, declared the end of any alliance with Indian Secular Front (ISF).^[21] Later on CPI(M) general secretary Sitaram Yechury said the electoral alliances was over after the polls, but the political understanding between Left, Congress and ISF will continue.^[22][23] Afterwards, ahead of 2024 Indian general election, ISF decided to contest alone in the Lok Sabha polls due to some differences in seat sharing and marks the end of alliance with Left and Congress.^[24] Thereafter, Sanjukta Morcha succeeded to LF-INC Alliance^[25] or Secular Democratic Alliance with the withdrawal of Indian Secular Front from the alliance.

More information Election Year, Overall votes ...

West Bengal Legislative Assembly election

Election Year	Overall votes	% of overall votes	Total seats	seats won/ seats contensted	+/- in seats	Sitting side
2021	59,122,500	8.68%	294	0 / 294	76	—

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Ahead of the 2021 West Bengal Legislative Assembly election, Indian Secular Front joined the alliance with Left Front and Indian National Congress.^[26] The alliance was announced in a rally of Left Front in the Brigade Parade Ground.^[27] The Left Parties will contest in 165 seats, Congress in 92 and ISF in 37 seats. Despite a spirited campaign, both the Left Front and the Indian National Congress drew a blank in the election with a considerable decrease in their respective vote shares. That was the first time when, the West Bengal Legislative Assembly was devoid of any Left Front or INC MLA.^[28] On the other hand, Indian Secular Front^{[lower-alpha 1]} wrested the Bhangar Assembly constituency from the Trinamool Congress. However, ISF left the alliance in 2024.

The Left Front supported Indian National Congress candidate Bayron Biswas for 2023 by-election in Sagardighi Assembly constituency.^[29] He defeated TMC candidate Debasish Bandopadhyay by a margin of 22,986 votes. However, Biswas later defected to the TMC.

On 2 March 2023, CPI(M) state secretary Mohammed Salim, in a press meeting, said that smaller anti-TMC and anti-BJP forces supported INC candidate Bayron Biswas. He also added that alliance of Left and Centrist forces and other parties will continue in 2023 Panchayat elections and 2024 parliamentary election.^[30] In May 2023, he said that Left, Congress and ISF are finalising seat-sharing arrangements for the 2023 Panchayat elections and will contest together in 2024 Parliamentary election.^[31]Later on, ahead of Lok Sabha polls ISF decided to contest independently breaking the relations with CPI(M) and Congress.^[32]

• Communist Party of India (Marxist), West Bengal
• Left Democratic Front
• Left Front (West Bengal)
• West Bengal Pradesh Congress Committee