The saga of setbacks for the former ruling party of West Bengal, Trinamool Congress, continued on Thursday with another leader, Rukmini Mallick, resigning from her Rajya Sabha membership.Rukmini, popularly known as Koel Mallick, tendered her resignation from the Rajya Sabha to Chairman CP Radhakrishnan on Thursday.She resigned with immediate effect. Mallick is the fourth TMC MP to quit the party’s membership. Earlier, Sukhendu Shekhar Ray, Sushmita Dev and Prakash Baraik had resigned.From the Lok Sabha, 20 TMC MPs also resigned and merged with the Nationalist Citizens Party of India, besides declaring support to the NDA.