Senior Congress leader Shashi Tharoor is exploring the possibility of running for the post of Congress president, though he is yet to take a final call on it, sources said. They said he has not made up his mind, but could take a call on it soon. While Mr Tharoor declined to comment on whether he would throw his hat into the ring, he has written an article for the Malayalam daily 'Mathrubhumi' calling for a "free and fair" election.