A coalition of the BJP its regional partners.
Bharatiya Janata Party
The Hindu nationalist BJP has governed India twice - for 13 days in 1996 and for 13 months before these elections with Atal Behari Vajpayee as prime minister both times.
It has now been returned to office at the head of the multi-party National Democratic Alliance with a clear majority.
The BJP has its roots in the militant Rashtriya Swayam Sevak Sangh, an organisation in the forefront of Hindu nationalism since 1925.
In the past 15 years, the BJP has consolidated its position as one of the main political parties in India (from 2 seats in 1984 to 182 in 1998 and 1999).
It came to prominence by backing the controversial move to build a temple over a mosque in the northern town of Ayodhya , but since coming to power, it has put the issue on the backburner and toned down its Hindu nationalism.
The hard-line Hindu party headed by Bal Thackarey was formed in 1966. The western state of Maharashtra remains its main support base where it formed its first government in 1995.
Janata Dal (United)
The party was formed with the merger of three regional parties, facilitated by veteran socialist leader, George Fernandes. A powerful ally of the NDA, it has 20 seats in parliament after a strong performance in Bihar. The JD(U) also has a presence in Karnataka.
The party, which is based in the southern state of Andhra Pradesh, led by Chandrababu Naidu and is the most powerful partner in the NDA with 29 seats. It was founded in 1985 by a former Telugu movie star, N T Rama Rao. Mr Naidu is now its undisputed leader, after leading the party to an impressive victory in elections to the state legislature which were held along with national elections. Mr Naidu is one of India's new generation leaders with an image as a dynamic reformer.
The Sikh Akali Dal of Punjab, the Tamil Nadu-based DMK and the Trinamool Congress party of West Bengal are some of the other parties in the NDA.