62-year-old Singh, who steadfastly announced Modi's name as BJP's Prime Ministerial candidate despite opposition from seniors like L K Advani, is going to be one of the trusted lieutenants of Prime Minister Modi with a major say in the functioning of the government.
Singh, a two-term BJP president, rose from a BJP activists in Gorakhpur, where he tought physics in a local college, to Chief Minister of politically crucial Uttar Pradesh and then Transport and Agriculture Minister in Atal Bihar Vajpayee government.
Elected to Lok Sabha from Lucknow, Singh has emerged from the ranks as a political heavyweight in the party largely due to his proximity to BJP's spiritual mentor RSS.
After taking over BJP's reins for the first time from Advani in December 2005, Singh sought to rebuild the party by focusing on basic Hindutva ideologies and said there would be "no compromise" on building the Ram Temple in Ayodhya.
Born on July 10, 1951 at Bhabhaura village in Uttar Pradesh's Chandauli district, Singh obtained MSc in physics from Gorakhpur University and was appointed lecturer in the K B Post degree college in Mirzapur in 1971.
Singh's association with Rashtriya Swayamsevak Sangh began in 1964 when he was only 13 year old. Even as lecturer he remained attached to RSS.
Rising step by step, he began his political innings with BJP's student wing Akhil Bharatiya Vidyarthi Parishad (ABVP) in 1969 as its organising secretary in Gorakhpur and rose to become the secretary of the then Bharatiya Jan Sangh's Mirzapur unit in 1974.