India, June 3 -- New Delhi

In a dramatic escalation of the crisis within the Trinamool Congress, at least 58 of the party's 78 MLAs have backed a rebel faction and moved against the leadership choice made by Mamata Banerjee for the post of Leader of Opposition, triggering what could become the biggest internal revolt in the party's history and raising existential questions over her grip on the party she founded.

The rebellion has unfolded at a politically awkward moment for Banerjee. Till last week, she was being projected, and projecting herself, as one of the tallest opposition leaders nationally and a possible face of opposition unity through the INDIA bloc. She had taken the initiative to push for an INDIA bloc meeting expected this...