The fledgling Aam Aadmi Party, or Common Man's Party, seized 28 of Delhi's 70 assembly seats just nine months after its formation. The Hindu nationalist Bharatiya Janata Party took first place with 31, while Congress was left with a meagre eight, a stunning decline from its previous 43.
All three ruled out entering into a governing alliance, leaving the capital in a leadership lurch and raising the possibility of new elections.
"Since I don't have the magic number of 36, I really cannot be part of the government formation in Delhi," the BJP's chief ministerial candidate, Harsh Vardhan, said after the election results were released late Sunday.
The Aam Aadmi Party was just as adamant about remaining on the outside.
"We are not going to form the government. We will sit in the opposition," top AAP member Yogendra Yadav said, according to the Press Trust of India news agency. "We have not got a majority, so it is very surprising that the No. 1 party (BJP) is not ready to form the government and telling us to do so."
The statements seemed to suggest that neither party would seek to form an insecure minority government that would have to rely on outside support. The idea of poaching Congress members appeared anathema to both parties bent on giving the capital's 17 million people a fresh start.
"I don't believe in coalition politics," said AAP's founder, Arvind Kejriwal, a former tax accountant who last year organized enormous anti-corruption protests that helped make India's systematic graft a subject of national outrage.
Delhi may be left with a nonpartisan caretaker administration until new elections can be held.
Experts said the AAP's success in the capital, which it hopes to repeat in nationwide elections next year, resulted from its singular focus on eliminating the corruption that plagues all levels of Indian government, from top officials embroiled in multimillion-dollar scandals to minor bureaucrats demanding token bribes for basic services.
The party chose a broom as its symbol, signifying its promise to sweep government clean.
It carried out a two-pronged campaign — reaching out to university professors, activists and students by social media while sending hundreds of volunteers into Delhi's poorest neighbourhoods.
The platform hit a nerve. Already reeling from runaway inflation and slowing economic growth, Delhi residents have become incensed over graft.
"What was incredible was the cross-section support for AAP from top-level elites to rickshaw drivers and house cleaners, from rich, poor, young and old," Delhi-based independent political analyst Arati Jerath said. "The dominant emotion was disillusionment with mainstream parties and traditional politics, with their cold, mathematical calculations over how to woo voters."
The Washington-based Global Financial Integrity institute estimates that bribery, corruption and kickbacks in India have resulted in at least $462 billion being secreted in foreign accounts since 1948. In 2010, Indians moved $1.6 billion overseas, according to the watchdog, which listed India in the top 10 countries sending illicit funds abroad.
Leaders of the Congress party — long the dominant force in Indian politics — pledged a period of soul-searching to analyze what went wrong in the elections. Congress also lost by landslides to BJP in the states of Rajasthan, Chhattisgarh and Madhya Pradesh.
"We will introspect and take action to rectify our mistakes," Congress leader Sonia Gandhi said, before calling an emergency meeting of party officials Monday.
Votes were still being counted in northeast Mizoram state, with results expected late Monday.
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