The Indian National Congress, again led by Manmohan Singh as its prime ministerial candidate, was returned to power, though without a majority of its own.¹

It won 206 of the 543 seats, short of the 272-seat mark needed for a majority.

The Bharatiya Janata Party finished second, taking 116 seats on 18.1% of the vote.

The INC's vote share — the slice of all ballots cast that went to one party or candidate — was 29.1%, which converted into 37.9% of the seats under India's first-past-the-post system.

The BJP and its National Democratic Alliance partners announced on 11 December 2007 that L.K. Advani would be their candidate for prime minister, formally electing him at a Delhi convention on 23 January 2008.²

In February 2009, Congress president Sonia Gandhi confirmed in the party magazine Sandesh that Manmohan Singh would be the United Progressive Alliance's prime ministerial candidate, the first time Congress had named its candidate ahead of an election.¹

The Election Commission announced that the 15th Lok Sabha election would be held in five phases between 16 April and 13 May, with counting on 16 May.³

In March 2009, Congress president Sonia Gandhi released the party's manifesto for the general election, emphasising the achievements of the UPA government over the preceding five years.⁴

On 7 April 2009, journalist Jarnail Singh threw a shoe at Home Minister P. Chidambaram at a Delhi press conference, protesting Congress fielding Jagdish Tytler and Sajjan Kumar, both accused over the 1984 anti-Sikh riots, as Lok Sabha candidates. On 9-10 April, Congress cancelled both their tickets.⁵

This was the first election held on constituency boundaries the Delimitation Commission had redrawn nationwide since 1976, using fresh census data. Delimitation — the official redrawing of constituency boundaries, which happens every so often as India's population shifts — changed district lines, seat shapes and reserved-seat assignments in most states, though the total number of seats stayed the same.⁶

INC's own seat count still grew, from 145 at the last election to 206 this time.

Turnout, the share of registered voters who actually cast a ballot, held roughly steady, up +0.2 pp to about 58.2%.

Tonk-Sawai Madhopur, Rajasthan saw the tightest finish of the election: the winner's margin — how far ahead the winner finished, in votes, over whoever came second — was 317 votes.

Vidisha, Madhya Pradesh saw the widest margin of the election, with the winner finishing 70.1% of the vote ahead of the runner-up.

Turnout peaked at Tamluk, West Bengal, where 90.3% of registered voters cast a ballot — the highest of any seat in the country.

Malkajgiri, Telangana was the largest constituency by registered voters anywhere in the country, with 23,43,050 names on its rolls.

Chennai South, Tamil Nadu drew the most candidates of any seat, 43 names on the ballot.

The Election Commission served notice over a Commonwealth Games-linked government advertisement during the campaign, stating that it "enumerates the achievements of the UPA Government" in violation of the model code of conduct.⁷