While the results from last weekend's elections will not have any bearing on the structure of the federal government, they sent a clear message to Modi that he was not invincible despite his party's strong showing in state elections since it was swept to power last year. They were also an indication of voters' frustration with endemic corruption.
Thousands of jubilant supporters of former tax collector Arvind Kejriwal and his Aam Admi Party, or Common Man's Party, beat drums and danced in celebration after India's Election Commission announced results Tuesday showing AAP's overwhelming win.
"Such a big mandate is very scary, and we should live up to people's expectations," Kejriwal told his cheering supporters, who yelled "Five years, Kejriwal!" and showered rose petals on him outside the party's headquarters in New Delhi.
Analysts said the scale of the defeat of Modi's Bharatiya Janata Party was a wake-up call for the government.
"Modi came to power in May making promises to people. But he has nothing to show on the ground even though eight months have passed," said Zoya Hasan, a political analyst with New Delhi's Jawarhalal Nehru University.
Kejriwal, whose promises of subsidized electricity also helped him win over voters, said the arrogance of leaders in Modi's party led to the BJP's poor showing. The party had been on a winning streak since demolishing the competition in national elections in May, with many attributing its success to Modi's charisma and his promises to increase economic growth and end corruption.
Kejriwal has made opposition to widespread graft a centerpiece of his political work. During a brief stint as NewDelhi's leader last year, he promised tough action against police officers and officials caught accepting bribes, and encouraged ordinary people to carry out sting operations by filming officials accepting bribes.
Modi said he spoke with Kejriwal on Tuesday, congratulating him and assuring the federal government's support in developing the capital.
"The AAP is going to write a chapter in history, in the history of politics," party supporter Nandidi, a homemaker who goes by one name, said while celebrating outside party headquarters.
With most votes counted, the Election Commission said the AAP won 66 out of 69 seats, with the BJP winning just three. The AAP was ahead in the one remaining constituency in the 70-seat assembly.
"Something dramatic has happened," a dejected BJP spokesman Nalin Kohli said.
The Congress party, which governed the capital for 15 years until its defeat in 2013, was nowhere on the radar.
One Congress party leader, Rita Bahuguna, said the vote amounted to "a referendum on Modi's arrogant style of functioning, communalizing politics in the country." She suggested the BJP's profile as a Hindu nationalist party had exacerbated communal tensions, leading to Hindu-Muslim clashes earlier this year in northern India, as well as encouraging a series of attacks on New Delhi churches.
The BJP had hoped to make a comeback in New Delhi, where it lost its stronghold 15 years ago, and many speculated the party decided to field former police officer and party outsider Kiran Bedi, a former Kejriwal ally, to strengthen the local leadership.
Bedi, who lost in an east Delhi constituency, apologized to her party's leadership and workers. "I couldn't live up to their expectations," she said.
Kejriwal, a graduate from the prestigious Indian Institute of Technology and a former income tax official, became hugely popular during his 2013 election campaign, which honed in on corruption as the country's greatest menace. While no party won an outright majority in that election, Kejriwal led a minority government for 49 days before resigning, leaving New Delhi under temporary federal government control.
While his resignation initially appeared to have left him in the political wilderness, Tuesday's results reflected his continued broad support, particularly among middle- and working-class voters.
"Democracy is winning today ... because an honest man is standing for us," 22-year-old student Pradeep Kumar said.