The Indian National Congress-I, the oldest among the political parties, became the nation's dominant political party, challenged for leadership only in more recent decades. In the 14th Lok Sabha (2004-2009), 145 members (out of 545), the largest contingent amongst all parties, serve in the house. The party is currently the chief member of the ruling United Progressive Alliance.
After Independence, the party remained in power for thirty continuous years before its first taste of electoral defeat (at the national level) in 1977.
The first serious challenge to the Congress hegemony came in 1967 when a united opposition, under the banner of Samyukt Vidhayak Dal, won control over several states in the Hindi belt.
Indira Gandhi was then challenged by the majority of the party leadership. The conflict led to a split, and Indira launched a separate INC. Initially this party was known as Congress (R), but it soon came to be generally known as the New Congress.
After the emergency in 1977, more Congress factions were formed, the one remaining loyal to Indira Gandhi being popularly known as Congress(I) with an 'I' for Indira. The Congress (I) was routed in the general elections by the Janata Party. The Congress party returned to power in the 1980 elections.
After Indira, her son Rajiv Gandhi, took over as Congress leader and led the party to victory with a large majority in the 1984 Lok Sabha elections. Following Rajiv Gandhi's assassination in 1991, PV Narasimha Rao became the prime minister.
In the 1990s, after gradually losing political influence, the Congress asked Sonia Gandhi to accept the position of Congress President. In 1998, Sonia Gandhi finally accepted the post of Congress President, in a move that may have saved the party from extinction.
In the 2004 general elections, the Congress alliance won the largest number of seats and got an assurance of support from the Left Front upsetting the Atal Bihari Vajpayee-led National Democratic Alliance.
Courtesy: Wikipedia