Kolkata, 1/3:Former Congress leader Kaustav Bagchi, who had resigned from the party a day before, joined the BJP on Thursday and vowed to fight against the TMC regime in the state.”Today, we are happy to welcome Kaustav Bagchi in the BJP,” party leader Suvendu Adhikari said at a programme here. West Bengal BJP president Sukanta Majumdar was also present. Bagchi resigned from the Congress on Wednesday, .