An alliance of Left Front and Congress have put up a tough fight against Trinamool Congress which aspires to come to power for a consecutive second term.
Altogether 163 candidates, including 21 women, are in the fray in those 31 seats of West Midnapore, Bankura and Burdwan districts.
Around 70 lakh people are eligible to cast their votes between 7 am and 6 pm.
Electorate in Bankura and Burdwan districts will have a tough time fighting the scorching sun as the districts are reeling under heatwave conditions with temperatures soearing above 40 degree Celsius.
Provisions for shade and drinking water have been made in many polling booths.
A multi-tier security system including two helicopters, quick response teams and flying squads has also been made.
The Election Commission has not provided information about critical polling booths and also refused to specify the number of companies of security forces deployed.
The Central Armed Police Forces have been mandated the responsibility of handling situation inside the booths, while the state police forces are involved in other jobs like maintaining queues and managing crowd.
Nearly 1,500 micro-observers, 23 general observers and over 36,600 polling personnel have been deployed in this phase.
Polling is being held at 8,465 polling stations amid tight security.
Of the about 70 lakh voters in this phase 33.6 lakh are women and 50 belong to the third gender.
Five more phases of polling will be held in the state till May 5.
Repoll in two booths of Bankura and West Midnapore districts, where polling was held in the first part of the first phase poll on April 4, is also being held today.
Besides TMC and the Left-Congress alliance, the BJP, which has only one MLA in the outgoing Assembly, has also fielded candidates from all the seats in the hope of making it a triangular fight.
Five-time CPI-M MLA from Narayangarh and Leader of Opposition Surjya Kanta Mishra, senior state Congress leader Manas Bhuniya from Sabang are among the major candidates in this phase.
91-year-old Gyan Singh Sohanpal, the senior most member in the Assembly, is in the fray again from Kharagpur Sadar seat where he is pitted against BJP state president Dilip Ghosh.