New Delhi, Jun 28 (IANS): United Progressive Alliance (UPA) candidate Pranab Mukherjee on Thursday filed his nomination for the July 19 presidential poll. Prime Minister Manmohan Singh, Congress president Sonia Gandhi as well as Samajwadi Party's Mulayam Singh Yadav and Rashtriya Janata Dal's Lalu Prasad were amongst the leaders present as Mukherjee filed his papers.