The BJP, in alliance with several other parties, was in power from 1998 to 2004, with Atal Bihari Vajpayee as the Prime Minister and Lal Krishna Advani as his deputy. It is the biggest constituent of the National Democratic Alliance which currently is in the opposition.
The BJP is a direct successor of The Bharatiya Jana Sangh (BJS, Indian People's Union), founded in 1951 by Syama Prasad Mookerjee, a nationalist leader, former Union Minister and freedom-fighter. It was considered the political wing of the Rashtriya Swayamsevak Sangh. But the fortunes of the young party took a dip in 1953, when Mookherjee was jailed in Kashmir by then Indian Prime Minister, Jawaharlal Nehru. After his death in custody, the BJS lasted for 24 more years, but never seriously challenged the power of Indian National Congress, the only well-structured political party since India's independence. It did however groom future political leaders like Atal Bihari Vajpayee and Lal Krishna Advani. In the Lok Sabha elections held in 1998 the NDA National Democratic Alliance obtained a simple majority. This time, the BJP (NDA) had allied with the AIADMK and the Biju Janata Dal besides its existing allies, the Samata Party, the Shiromani Akali Dal and Shiv Sena. Outside support was provided by the Telugu Desam Party. The NDA had a slim majority, and Vajpayee returned as Prime Minister.  But the coalition ruptured in May 1999 when the leader of AIADMK, Jayalalitha, withdrew her support, and fresh elections were again called. On October 13, 1999, the BJP-led NDA won 303 seats. The BJP won an all-time high of 183. Vajpayee became Prime Minister for the third time in his life, and Advani became the Deputy Prime Minister and Home Minister. This NDA Government lasted its term of five years. Vajpayee and his economic team, led by Finance Minister Yashwant Sinha, continued the policies initiated by the previous Congress Government under P V Narasimha Rao and Manmohan Singh, pushed through major privatizations of big government corporations, the liberalization of trade under World Trade Organization rules, opening the skies to commercial airlines, foreign investment and ownership and allowed private companies such as Mahindra World City and Reliance to build Special Economic Zones where property developers could build new cities with world-class infrastructure for factories that export products. The BJP and the NDA suffered a shock defeat in the general elections in 2004, and failed to muster a parliamentary majority. A.B. Vajpayee passed on the prime ministership to Dr. Manmohan Singh of the Congress Party, and its United Progressive Alliance. In 2009 general elections, BJP again faced defeat and its strength in Lok Sabha reduced to just 116 seats. The unexpected defeat of BJP is attributed to bad performance of party in Uttar Pradesh, Gujarat, Rajasthan, Uttarakhand and Madhya Pradesh.