The significant phase will not only decide which party will form the government, but will also determine if the CPI(M)-led Left retains its strongholds or the TC-Congress alliance makes gains.
Polling will be held in 63 Assembly constituencies spread over four districts -- Hooghly, Howrah, East Midnapore and parts of Burdwan.
Trinamool Congress had made major gains in the 2009 Lok Sabha elections in the four districts capturing six of the eight seats.
The seats include Singur in Hooghly and Nandigram in East Midnapore which have changed the political scene in the state after the anti-land acquisition movement by the Mamata Banerjee-led Trinamool Congress.
Over 1.26 crore voters will decide the fate of 366 candidates including Industry minister Nirupam Sen and Higher Education minister Sudarshan Roy Chowdhury and five other cabinet members.
Altogether 20,000 EVMs will be used in 15,711 polling stations, state chief electoral officer Sunil Kumar Gupta said.
Tight security arrangements have been made with the deployment of a huge contingent of security forces including Central forces in the districts going to the polls tomorrow, he said.
Other ministers in the fray include Food Processing minister Mohanta Chatterjee, Minister of State for Information and Culture Soumendranath Bera, Technical Education minister Chakradhar Maikap, Agriculture minister Naren Dey and Fire Services minister Pratim Chatterjee.
Three former IPS officers Rachpal Singh, Haider Aziz Sawfi and Sultan Singh have been fielded by the Trinamool Congress candidates in this phase.
Of the six phases of the elections, three were held on April 18, 23 and 27. The fifth phase will take place on May 7 and the sixth and last on May 10.