While Congress lost two seats, ruling Trinamool failed a major popularity test since 2011 Assembly polls by coming third in two segments.
With the Left Front managing to snatch away one seat, it became clear that the Front had benefited from the division of votes between Congress and Trinamool.
Though Congress managed to retain Rejinagar seat in Murshidabad district with Rabiul Alam Choudhury as its candidate, the party lost English Bazar in Murshidabad district to Trinamool's Krishnendu Narayan Choudhury and Nalhati seat in Birbhum district to Left Front's Dipak Chatterjee.
The by-polls, which was a test of popularity for all the three parties after the break up of Congress and Trinamool, seems to have sent out a message that both the parties need to stick together if they want to keep the Left Front at bay.
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With the defeat in two Assembly segments, Congress tally in West Bengal Assembly dipped from 42 to 40. The defeat in English Bazar segment of Malda was a loss of face for the party as it was considered a party stronghold.
Riding on the legacy of late Congress leader Barkat Ghani Khan Choudhury 'Barkatda', the Congress had earlier performed admirably during a substantial part of the 34-year Left regime.
Krishnendu is currently serving as a minister in the Trinamool government.
Mamata Banerjee's party previously in its 13 years of existence has failed to make much dents in the Congress bastions of North Bengal such as Malda, Murshidabad and Uttar Dinajpur.
Political analysts feel Trinamool was able to win the English Bazar seat with a handsome margin of 20,000 votes only due to Krishnendu's credibility as a mass leader of the area.