From an unmarked office in Gandhinagar, the capital of Modi's home state of Gujarat, the young men and women, some on sabbaticals from firms like JP Morgan and Deutsche Bank, worked on turning a fragmented parliamentary election involving 543 seats into a presidential-style referendum on candidate Modi. (Agencies)
In doing so, Modi cut loose from the traditional Delhi-based structure of his Bharatiya Janata Party (BJP) and its apparatchiks and adopted the language of a youthful country eager for change, using everything from holograms to WhatsApp.
The modern approach worked: just an hour into the counting of votes on Friday, it was clear that the 63-year-old Modi was heading for a stunning victory with the strongest mandate any Indian government has enjoyed for 30 years.
By midday, the BJP and its allies were leading the count in 329 parliamentary seats, far ahead of the 272 majority required to rule. Even on its own, the BJP had crossed the required mark.
So great appears to be the desire for change, especially among India's middle class some 300 million strong, and so firmly has Modi stayed on message, that a dark chapter of violence against Muslims on his watch has mattered less and less to many voters.
Modi, a Hindu nationalist, has long faced allegations that he looked the other way when Hindu mobs went on a rampage of revenge against Muslims in Gujarat after a train carrying Hindu pilgrims was torched in 2002.
He has denied the allegations and a Supreme Court ordered inquiry absolved him of responsibility.
Modi has refused calls for remorse for the lives lost, most of them from the sizeable Muslim minority of more than 150 million people. Instead he has donned the mantle of an economic modernizer, building on Gujarat's mercantile traditions.
In recent years, the state Modi governed since 2001 has been compared with Guangdong province, the spearhead of China's economic revival.
Since Modi took control, Gujarat has led the nation in GDP growth. It accounts for 16 percent of industrial output and 22 percent of exports, despite having 5 percent of its population.
Under his stewardship, farmers and industry have been assured uninterrupted power, albeit at high rates, and bureaucratic controls slashed.
A Central government-ordered study last month said that it had the best land acquisition policies in place, among all of India's 29 states in terms of ease of doing business.
Land, by far, has been the single biggest hurdle around the country, holding up 90 percent of infrastructure projects.
Gujarat's highways are India's fastest, a far cry from the potholed roads in the northern belt, and its ports are among the busiest.
But repeating that success nationally presents significant challenges in a country with a complex federal structure, a bureaucracy more wedded to socialist controls than reform and a growing gap between rich and poor among its 1.2 billion people.
India must create 10 million jobs a year, four times the pace of the last 5 years, to absorb youth into the workforce.
And unlike China, India is not centralized. Modi will have a fight on his hands to gain full cooperation from many state governments, which he needs to implement his agenda nationwide.
Some have said that the pace of development in Gujarat has caused environmental damage and threatened small communities, and that crony capitalism flourished under Modi's unquestioned rule.
Critics also say it lags behind other states in social indicators such as mortality rates.
But the criticisms have failed to stick.
"Modi has led from the front. None of this would have been possible, but for him," said Rajnath Singh, the president of the BJP and a close associate.
'Purveyor of dreams'
Modi, with his neatly-trimmed white beard, was the only face of the campaign. He has covered 3,00,000 km since being named the BJP's prime ministerial candidate in September, addressing 457 meetings. When he could not show up, he appeared as a hologram.
"He has become a purveyor of dreams," said Sanjay Gupta, a former state bureaucrat who quit to go into business and start a chain of hotels.
"It’s hard to see how he can meet all the pent-up aspirations without re-engineering the system," said Gupta.
The son of a railway station tea-seller, Modi has humble roots which he reminds voters are in contrast to the privileged upbringing of the Nehru-Gandhi dynasty and its scion Rahul Gandhi, who led the campaign for the ruling Congress party.
Modi left home after school, virtually cutting off all family ties as he found his calling in the Rashtriya Swayamsevak Sangh, a right wing organization that serves as the ideological parent of Hindu groups and the BJP.
Its members, who hold military-style drills and indoctrination sessions at grounds across the country each morning, seek to make India a great power, militarily strong and economically prosperous.
Kishore Makwana, a member of the RSS who used to ride pillion on Modi's scooter during his days as a RSS propagandist, said Modi would sometimes sleep on the pavement because he had arrived too late at a host's house and thought it impolite to knock at that hour.
"He hasn't forgotten those days. He is firmly rooted," Makwana said.
One thing Modi has never talked about publicly is his failed marriage, which reportedly took place when he was in his teens and after the couple had been spoken for by their parents in the tradition of that time.
Last month he disclosed for the first time that he was married to Jashodaben in an election declaration after leaving the form vacant in two earlier elections he fought.
Modi, according to unofficial biographies, did not accept the marriage and may have left his home for that reason. Jashodaben went back to her brother's house where she has lived and hasn't met her husband for more than 40 years.
Modi, said to be a loner, has kept away from his immediate family too, meeting his mother and brothers only occasionally.
In an interview, he has said that his real education took place in the RSS and that he owed everything to the organization.
To some, his background in the Hindu group and his handling of the riots in Gujarat remain a cause of concern. Critics say that the RSS is deeply opposed to Muslims and that its objective of a Hindu India was a challenge to India's secular traditions.
The organization says it only opposes appeasement of any community.
"I find the idea of Narendra Modi as the prime minister of this country deeply repugnant. It is an assault on the idea of India, because of what he represents and what his track record has been," said former Congress federal minister Mani Shankar Aiyar, one of Modi's most trenchant critics.
Within Gujarat itself, critics point to the segregation that has taken place over the last decade. For Muslims it is difficult to buy property in areas dominated by Hindus, forcing the community's fast-growing urban middle class to live in cramped and decrepit corners of cities.
"Modi is set to govern all of India, the 150 million Muslims included, and there is reason to be cautious," said Ruchir Sharma, head of emerging markets at Morgan Stanley.
From an unmarked office in Gandhinagar, the capital of Modi's home state of Gujarat, the young men and women, some on sabbaticals from firms like JP Morgan and Deutsche Bank, worked on turning a fragmented parliamentary election involving 543 seats into a presidential-style referendum on candidate Modi.