Introduction:
Coalition politics refers to the formation of alliances or partnerships between different political parties to gain a majority in the government. In India, coalition politics became prominent during the period from 1989 to 2014.

Reasons for the Emergence of Coalition Politics:
1. End of Single Party Dominance: Prior to 1989, the Indian National Congress (INC) enjoyed a dominant position in Indian politics. However, with the emergence of regional parties and the decline of the Congress party's popularity, the era of single-party dominance came to an end.

2. Fragmentation of the Party System: The rise of regional parties led to a more fragmented party system in India. These regional parties represented the diverse interests and aspirations of various states and communities. As a result, no single party could secure a majority on its own, leading to the need for coalition governments.

3. Growth of Coalition-Oriented Politics: The Mandal Commission report in 1990 and the implementation of the Mandal reservations for Other Backward Classes (OBCs) led to the emergence of identity-based politics. Parties started forming alliances based on caste, religion, or regional affiliations to consolidate their vote banks.

Key Phases of Coalition Politics:
1. Janata Dal Era (1989-1991): The National Front government, led by V.P. Singh, came to power in 1989 with the support of several regional and left-wing parties. This marked the beginning of coalition politics at the national level.

2. United Front Governments (1996-1998): The United Front, a multi-party coalition, formed governments under Prime Ministers H.D. Deve Gowda and I.K. Gujral. These governments were supported by the Congress party from outside.

3. National Democratic Alliance (NDA) (1998-2004): The Bharatiya Janata Party (BJP) led the NDA coalition, which consisted of several regional parties. Atal Bihari Vajpayee served as the Prime Minister during this period.

4. United Progressive Alliance (UPA) (2004-2014): The Congress party formed the UPA coalition with support from various regional parties. Manmohan Singh served as the Prime Minister for two consecutive terms.

Advantages and Disadvantages of Coalition Politics:
Advantages:
- Reflects diverse interests and regional aspirations.
- Promotes power-sharing and consensus-building.
- Prevents the concentration of power in a single party.

Disadvantages:
- Can lead to instability and frequent elections.
- Compromises on policy decisions to accommodate the interests of coalition partners.
- Lack of accountability as blame can be shifted between coalition partners.

Conclusion:
Coalition politics became prominent in India from 1989 to 2014 due to the end of single-party dominance, the fragmentation of the party system, and the growth of coalition-oriented politics. This period witnessed the formation of various coalition governments, including the National Front, United Front, NDA, and UPA. While coalition politics reflects the diversity of Indian society, it also poses challenges in terms of stability and decision-making.