At about the age of 10 he started attending meetings of the Rashtriya Swayamsevak Sangh (RSS), a vast and influential Hindu revivalist conservative movement that has been banned three times in India. He joined formally only at a later date.

His first job for the RSS involved sweeping for a senior official. Later assigned to the Bharatiya Janata Party (BJP) - the affiliated but independent political party - Modi forged his own path, ousting opponents one by one until he was appointed chief minister of Gujarat in 2001.

He went on to win three elections there, largely rooted in the consistent economic growth in the state, and these victories have given him a platform from which to outflank the entrenched old guard of the BJP itself.

Across India, thousands of RSS followers campaigned for Modi ahead of his victory, which saw his BJP win the first parliamentary majority in 30 years.

That effort, as well as longstanding ties with the BJP, raises questions about how much the group will influence its most famous alumnus, who will be sworn in as India's next prime minister tomorrow. "Since a person from RSS is going to be prime minister, we expect he will work not only for the nation, but also for RSS," said Rajeev Varma, a 23-year-old engineering student. "Obviously we feel proud."

But experts say Modi could disappoint the group and its four-and-a-half million members, aware his prospects depend primarily on meeting pledges of growth and development.

"He has to win on the economy, and he will be judged on that," said Christophe Jaffrelot, an expert on the Hindu nationalism movement.

"What if he fails to relaunch the economy? The Hindutva (Hindu nationalist) plank is the plan B."

The charges that Modi allowed, or even encouraged, mob violence in 2002 in Gujarat - which he denies and which a supreme court investigation found were not supported by the evidence it was able to examine - reinforce his status as a man who is separate from the political establishment.

About 1,000, mainly Muslims, died after 59 Hindu pilgrims were killed in an arson attack. A similar stain on a reputation would have finished the career of some. For many years, Modi was a political pariah, internally as well as internationally. Only in the last two years have the UK, the EU and finally the US ended boycotts.

Hartosh Bal Singh, a political writer, argues Modi's record, in 2002 and subsequently, boosted his appeal to a large right-wing Hindu constituency who "are not unsympathetic to the view that [Hindu] culture has not received its due and that here is a man who can stand up for Hindus and assert that they can and will rule in their country".

If Modi largely escaped judicial censure, at least one close aide was convicted of having a role in the violence. Some campaign rhetoric fuelled fears that Modi might either be prejudiced himself or happy to exploit the prejudices of others.

Millions of India's Muslims fear Modi's landslide victory will fuel religious discrimination, intolerance and even bring bloodshed. But some are also prepared to give him a chance.

"My hopes have been rekindled. I am looking forward to better days under his rule," said Abdul Salaam, 29, a Muslim tailor in Varanasi, a Hindu holy city which has a sizeable Muslim community.

Muslim widow Parveen Banu, whose family was killed in communal riots in Gujarat, said the BJP leader would not dare turn against Muslims after weeks on the campaign trail preaching national unity. "Of course Modi hates Muslims. But as prime minister, can he really afford to show it?" Banu asked.

"Plus, he has spoken of cultural unity and he has to live up to our expectations and I believe he will. He's not crazy."

Modi stands in stark contrast to Rahul Gandhi, the 43-year-old great-grandson, grandson and son of former prime ministers.

The 63-year-old is celibate, has no children and is ascetic and honest. He has had no powerful relatives looking out for him.

He has not been to the best Indian schools and is not interested in big cars or showy status symbols. The nearest to luxury is a taste for thin-rimmed designer frames for his glasses.

He is a small-town boy who has little of the cultural capital of the old guard within his own party, let alone the grandees of the Congress party.

He is not comfortable speaking in English, communicating with his close associates in Gujarati and addressing crowds across the country, very effectively, in Hindi.

He is also from the caste categorised as Other Backwards - as are perhaps a third of his compatriots. Few Indian politicians have these characteristics and none combines them like Modi. The rapid rise of this outsider from provincial politician to a prime ministerial contender who launched an unprecedented effort to win himself the highest executive office in the land has rattled Delhi's powerful elite.

Early in the election campaign Mani Shankar Aiyar, a veteran congress politician who was educated at the Doon school, St Stephen's college and Cambridge, derided Modi's origins as a tea-seller, saying he should serve Indian's favourite beverage at party meetings.

Aiyar, who styles himself as something of a wit, has defined democracy in America as "the right of the lower orders to be rude to their social superiors".

It is this kind of attitude - or the paternalism of the Gandhis - that seems increasingly anachronistic in India and is one reason for the space that has opened up for Modi.

Political commentator Ashok Malik said the election was determined by the intersection of two major changes - the flow of rural Indians into towns and the first impacts of the world's biggest younger generation.

Both factors are drastically changing the country, bringing new values, behaviours and conflicts.

They are also pushing up expectations, which the outgoing Congress-led government was unable to fulfil, to stratospheric altitudes.

It is unclear whether Modi will be able to do so either.

But those expectations, and the fear that they may be disappointed in coming years, is why Modi's fusion of nationalism, apparent executive ability and culture is so powerful.

Each facet promises a different resurgence - of India as a great nation on the world stage, secure at home and respected abroad; of clean and competent government providing efficient services, honest administration and jobs; and of a particular vision of authentic local identity, of what it is to be an Indian, that does not necessarily fit perfectly with the old idea of a pluralistic, secular India.

Modi's message also includes social mobility, and his characterisation as the patriotic, but poor, provincial nobody.

Now in power, however, he will need a new narrative.