Noting that he has his roots in Bengal, Mukherjee said that the President was above party politics and was an upholder of the Constitution.
"It is in this spirit that I seek your valuable support in this election," he said, adding that he is honoured that UPA allies and other parties have considered him worthy for the post.
Recalling the rich legacy left by past presidents of India like Rajendra Prasad and Zakir Hussain, he said the Constitution of India remained pro-poor.
However, Trinamool MP Derek O'Brien told PTI tonight that a personal touch was missing in the letter as it carried a printed signature and was sent by post with a Rs 5 stamp on it.
Party sources said the letter should have been sent to party supremo Mamata Banerjee, who would take the final decision.
Banerjee has already said that she would make known her decision three days before the Presidential polls on July 19.