UPA-Left candidate Pratibha Patil today filed her nomination papers for the Presidential poll - the first nominee of a major political combine to enter the July 19 election fray.With Prime Minister Manmohan Singh and Congress president Sonia Gandhi by her side, 72-year-old Patil filed two sets of documents before the Returning Officer and Lok Sabha Secretary General P D T Achary in the Parliament House.It was a show of unity of the UPA-Left alliance as top leaders Lalu Prasad, Sharad Pawar, Ram Vilas Paswan, T R Balu, Ramdas Athawale, Sitaram Yechury, Gurudas Dasgupta and Abani Roy were also present on the occasion.If elected, Patil, who resigned as Rajasthan Governor on Thursday, will become the first woman President in independent India.NDA has already declared support to Vice President Bhairon Singh Shekhawat as an independent candidate, but he has not yet formally announced his nomination for the top post.Patil, with her family members, also visited Rajghat, the memorial of Mahatma Gandhi, to pay tributes to the Father of the Nation.