What is a defining characteristic of the governments formed at the centre since the 1989 elections?

All have been coalition or minority governments.

From May 1998 to June 1999, a coalition government was established, and subsequently, it was re-elected in October 1999. Throughout this period, Atal Behari Vajpayee held the position of Prime Minister for both terms of the National Democratic Alliance (NDA) governments. Notably, the government that materialized in 1999 successfully completed its entire term in office.

Following the elections of 1989, a notable shift towards coalition politics became prominent in India's political landscape. Since that juncture, the country has seen eleven different governments at the national level. These administrations have predominantly taken the form of either coalition governments or minority governments that receive support from other parties, without formally joining the government. This marked a new phase in Indian politics, where the formation of any government hinged on the participation or backing of various regional parties.

This trend was evident in several key instances, such as the National Front's establishment in 1989, the United Front's governance in 1996 and 1997, the NDA's formation in 1997, the BJP-led coalition in 1998, the NDA's re-emergence in 1999, and the United Progressive Alliance (UPA) that governed in 2004 and 2009. However, this trend underwent a transformation in the year 2014.