Mr Tharoor will file his nomination for the October 17 election today.
Ahead of filing his nomination for the post of Congress president, senior party leader Shashi Tharoor on Friday paid tributes to former prime minister Rajiv Gandhi.
Taking to social media, Mr Tharoor shared photos of him standing next to the sculpture dedicated to the former prime minister at Raj Ghat.
"Paid tribute to the man who built India's bridge to the 21st century this morning," he wrote on Twitter.
"'India is an Old country but a young nation... I dream of India Strong, Independent, Self-Reliant and in the front rank of the nations of the world, in the service of mankind - Rajiv Gandhi'," he added.
In another tweet, Mr Tharoor shared pictures of him bowing down to Mahatma Gandhi's memorial.
"Paid homage to the Great Soul at Rajghat before embarking on my campaign," he wrote.
"'In a gentle way, you can shake the world. - Mahatma Gandhi'," he added.
Mr Tharoor will file his nomination for the October 17 election today along with Mallikarjun Kharge, the Leader of Opposition in Rajya Sabha.
Mr Tharoor was among the 23 senior Congress leaders -- now known as G-23 -- who had written a letter to Congress president Sonia Gandhi in 2020, seeking sweeping reforms in the party.
This is the first Congress president election in 20 years. Members of the Gandhi family have refused to contest the polls, making way for other senior leaders to head the party.