The Indian National Congress, led by party president Sonia Gandhi, returned to power after five years in opposition.¹

It won 145 of the 543 seats, more than any other single party.

That left it short of the 272-seat majority mark, a hung house — a result where no single party wins enough seats to govern alone.

The Bharatiya Janata Party finished close behind, with 138 seats on 22.2% of the vote.

It governed instead through the UPA, an alliance — a group of parties that team up to fight an election together, and share power afterward if they win enough seats between them — holding 158 seats in all.

In January 2004 the governing BJP-led alliance promoted the slogan 'India Shining,' developed by advertising firm Grey Worldwide in consultation with Finance Minister Jaswant Singh. The Caravan reported the government spent more than Rs 100 crore publicising it in the months before the poll.²

On 6 February 2004 President A.P.J. Abdul Kalam dissolved the 13th Lok Sabha on the advice of Prime Minister Atal Bihari Vajpayee's cabinet, calling elections roughly seven months ahead of schedule. The Election Commission then set a four-phase schedule, with polling on 20 April, 26 April, 5 May and 10 May, and counting on 13 May.³⁴

On 5 April 2004 Rahul Gandhi, son of former prime minister Rajiv Gandhi, filed nomination papers as the Congress candidate for Amethi, marking his entry into electoral politics. On 6 April, the BJP and the AIADMK told the Election Commission they would keep raising Congress president Sonia Gandhi's foreign origin as a campaign issue.⁵¹

On 8 April, NDA leaders led by Vajpayee met in Delhi to adopt the alliance's manifesto, 'Agenda for Development and Good Governance.'⁶

Voting itself changed nationwide before the results did: this was the first election held with electronic voting machines in every constituency, replacing paper ballots.⁷

Indian National Congress climbed from 114 seats last time to 145 seats this time.

Nationwide, 282 of the 543 comparable seats changed hands.

The single biggest swing ran from BJP to INC, 54 seats moving that way.

Turnout — the share of registered voters who actually cast a ballot — slipped -1.3 pp from the previous election, to about 58.0%.

Lakshadweep, Lakshadweep saw the tightest finish of the election: the winner's margin — how far ahead the winner finished, in votes, over whoever came second — was 71 votes.

Arambagh, West Bengal went the other way, with the winner finishing 61.4% of the vote ahead of the runner-up — the widest margin of any seat that year.

Turnout peaked in Nagaland, Nagaland, where 91.7% of registered voters cast a ballot — the highest of any seat that year.

Outer Delhi, Delhi was the largest constituency in the country by registered voters, with 33,68,399 names on its rolls.

Madras South, Tamil Nadu drew the most crowded ballot of the election, with 35 candidates standing.

The TRS won Lok Sabha seats for the first time at this election.

The 84th Constitutional Amendment, passed in 2001, froze the number of seats each state sends to the Lok Sabha and state assemblies at their 1971-census levels until the first census after 2026.⁸

The 91st Constitutional Amendment, effective from January 2004, closed a loophole that let lawmakers dodge anti-defection penalties by forming breakaway groups, and capped cabinet sizes at 15% of a legislature's membership.⁹

The Supreme Court had also, in 2003, ordered mandatory candidate-disclosure affidavits, requiring every contestant to declare criminal cases, assets, liabilities and educational qualifications.¹⁰