Over the past three years, Arvind Kejriwal has emerged as the angry young man of Indian politics - a rabble-rousing campaigner who has relentlessly attacked the political establishment for corruption and bemoaned the failure of the country's representative democracy.
On Saturday the former Indian tax official rejoins the establishment, being sworn in as the chief minister of the New Delhi state government after a stunning electoral upset this month by his year-old Aam Aadmi party, which won 28 of the 70 seats in the legislative assembly.
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Mr Kejriwal's challenge now is to prove that the AAP - its name means "Common Man" party - was more than just a protest vote for New Delhi residents and can actually provide credible governance of India's congested capital city and its 12m people.
The party's performance will be closely watched across India as the country gears up for a fierce parliamentary election battle between the ruling Congress party and the opposition Hindu nationalist Bharatiya Janata party.
"The opportunity is to demonstrate, even if briefly, even if as a window, what an Aam Aadmi government can look like to the rest of the country," says Yogendra Yadav, a respected psephologist and one of the main leaders of the fledgling party.
Analysts say that with its strong performance in New Delhi's state assembly polls, the AAP has emerged as a wild card in parliamentary polls, due by May, offering an alternative to voters fed up with the incumbent Congress party but uncomfortable with the BJP and its controversial prime ministerial aspirant, Narendra Modi.
"The Aam Aadmi party victory in Delhi shows that when there is an alternative, voters are likely to vote for it," says Prem Shankar Jha, author of India & China: The Battle between Soft and Hard Power. "Many who are angry with Congress don't want to vote for the BJP . . . They will vote for the Aam Aadmi party because it is there - because they hate the others."
Yet Mr Kejriwal faces a formidable task as he seeks to move the AAP past combative rhetoric to something more constructive.
"The task of delivering the goods in a sprawling and unwieldy city like Delhi is monumental," the Hindustan Times said in an editorial. "Here, the AAP has little experience and will have to learn on the job."
The tabular content relating to this article is not available to view. Apologies in advance for the inconvenience caused. The party will be running the city administration with a minority government, dependent for its survival on the outside support of the Congress party, whose past misdeeds - including alleged corruption during the 2010 Commonwealth Games - the AAP has vowed to zealously prosecute.
It's hardly a recipe for stability, as AAP leaders readily admit. "If the rug is pulled from under our feet - if our government collapses on that ground, it collapses," Mr Yadav says. "We are ready for that on day one."
Analysts say that Congress support for the AAP is likely to be withdrawn within a few months, forcing a rerun of the New Delhi state election at the same time as the 2014 parliamentary polls.
Implementing the AAP's populist agenda itself poses difficulties. The party has promised to provide 700 litres of free water daily to every family in Delhi and to halve their power bills, which Mr Kejriwal, an engineer, has long claimed were inflated by the private power providers.
It is also seeking to radically reshape how business is done in the Indian capital - changes Mr Kejriwal says are necessary to tackle deep-seated corruption. "The system will soon overpower us and we will get sucked into it. So we will have to change the system completely," Mr Kejriwal said in a recent interview with The Times of India.
The AAP envisions a significant devolution of power to about 2,720 neighbourhood councils, authorising them to decide on development in their areas as well as clear payments for public works, such as road repairs. It is unclear how this would work in practice.
At its core, the AAP's political programme and its stunning electoral success are a reaction to India's political elites, who court voters once every five years in the polls then retreat to their colonial-era government bungalows, treating their electoral victory as a blank cheque in the absence of a system to hold them accountable.
This extreme disaffection with the political establishment is not just among the poor, but has cut across classes, as illustrated by Mr Kejriwal's own landslide victory over New Delhi's three-term chief minister, Sheila Dixit, who hails from the city's most affluent constituency.
"The elite voted for a party called a Common Man party," says a businessman who lives in the area but asked not to be identified. "This is a big revolt against corruption, and also the arrogance of the ruling politicians."
Reflecting the AAP's determination to reshape India's political culture, Mr Kejriwal has promised that neither he nor his ministers will take up residence in the grand bungalows to which they are entitled. He also has eschewed other privileges, such as the right to have a red siren atop his car, allowing him to zip through the city's notorious traffic.
Yet New Delhi's residents will be looking for more than symbolic gestures. Some fear that new AAP officials may be tempted into corruption, or even be set up by their political rivals, tarnishing the party's clean image.
"If they fail, or if other parties make them fail," says the Delhi businessman, "some of the romance of the revolution may go."
