The Bharatiya Janata Party’s dramatic win in the West Bengal election promises to not only reorient the political direction of the state but also influence India’s relations with Bangladesh. For a year and a half after the ouster of Sheikh Hasina as Bangladesh prime minister, New Delhi’s ties with Dhaka were at their lowest ebb in decades. Dhaka accused New Delhi of sheltering Ms Hasina despite her alleged crimes by hosting her in exile. India accused Bangladesh of allowing atrocities against Hindus and other religious minorities to go unchecked. Bangladesh’s growing warmth with Pakistan upset India further. Even people-to-people relations were adversely affected on account of visa restrictions. An election — in Bangladesh — helped the neighbours break that downward spiral. The Bangladesh Nationalist Party and its leader, Tarique Rahman — the winners — reached out to India and promised an inclusive governance domestically. Since that landslide victory in February, bilateral relations have improved, with senior officials from both sides exchanging visits. Now, another election — in Bengal — could pose a fresh test for that upward trajectory in ties.

One of the BJP’s favourite electoral catchphrases is ‘double engine sarkar’. In essence, the argument goes that the same party in power nationally and in a state is better for governance. With its Bengal win, that idea will be challenged in the theatre of foreign policy. For 14 years, Mamata Banerjee and her Trinamool Congress opposed the Teesta water-sharing agreement with Bangladesh, which India, under governments of the United Progressive Alliance and the National Democratic Alliance, has been keen on signing. Earlier, New Delhi would explain to Dhaka that the federal nature of Indian democracy had tied its hands when it came to inking the treaty. That justification will no longer work. Indeed, this is an opportunity for the Indian government to build a long-term bridge with Bangladesh by finalising a deal on the Teesta. But the BJP’s rhetoric on illegal Bangladeshi immigrants in Bengal and beyond also threatens to poison the green shoots that have emerged in bilateral ties. Religious polarisation, one of the potent electoral weapons of the BJP, may also make it difficult for Dhaka to do business with New Delhi. Narendra Modi and the Bengal chief minister, Suvendu Adhikari, have a historic opportunity to rebuild India-Bangladesh ties. Bengal has given them the mandate. They must use it wisely.