West Bengal Chief Minister Mamata Banerjee on Monday left for Lucknow to campaign for Samajwadi Party (SP) and gave the call to defeat BJP in the coming Uttar Pradesh assembly polls. Banerjee left for Lucknow this evening. She will be holding a joint press conference with Akhilesh Yadav, the national president of SP and a virtual rally in Lucknow on February 8, according to sources in the party.