Why Mamata Banerjee proposed Mallikarjun Kharge as I.N.D.I.A.`s PM Face?

Meeting of the opposition alliance 'India' was held on 19 December. There will be demonstrations across the country on 22 December. If sources are to be believed, Kharge can be made the PM candidate from the opposition. Mamata Banerjee had proposed the name of Mallikarjuna. After which it was told that Nitish and Lalu got angry.