A day after being selected by West Bengal Chief Minister Mamata Banerjee as the chairperson of the newly constituted Tribal Development Committee (TDC), former CPI(M) leader Ritabrata Banerjee tweeted: “Humbled to be a part in Didi’s [Ms. Banerjee] endeavour of transforming the State.”Mr. Ritabrata, once a fiery student leader and CPI(M) MP, was expelled from the party last September. Observers read his appointment as an induction into the Trinamool Congress.He, however, refused to be drawn into political speculation. “I am an Independent MP and continue to work in that capacity,” he told The Hindu.Challenge to BJPHe did, however, echo nearly all defectors on the future of politics in Bengal, when he said, “I have said for a long time that Mamata Banerjee is the only person to challenge the BJP at the State and at the national level; strengthening her is important.”Former CPI(M) MP from Murshidabad Moinul Hassan, who quit the party on Saturday, went a step further to suggest that an alliance of Trinamool Congress, CPI(M) and Congress was “vital.”“Many are asking me whether the TMC and CPI(M) can be part of the same alliance. If Akhilesh Yadav and Mayavati can come together, it can be emulated in Bengal,” said Mr. Hassan.At least five Congress MLAs and few CPI(M) leaders are expected to join the Trinamool Congress on July 21. Sabina Yeasmin, MLA from Malda, whose name featured in the list of the MLAs, has spent a decade with the Congress.“The way BJP is growing in Bengal, it is now imperative to join the TMC,” she said. She added that party president Rahul Gandhi had asked her “to wait before taking a final decision” at his meeting with restive MLAs on Friday.