“Congress has been in power since independence,” he said. “They say all the right things, but look at the condition of the country — other countries have come much farther in the last 60 years. Why don’t we have better medical facilities, educational facilities, roads? Why? Who is answerable for this?”

In the months that followed, I heard versions of these questions in villages, in dusty cantonment towns, in the hybrid spillover communities at the edges of great cities.

This is vast, churning, aspirational India. Farmers I met in the state of Andhra Pradesh were spending every last rupee they earned, or incurring terrible debts, to send their children to private schools advertised on billboards on the highway in the hopes that they would somehow end up with an office job — anything, really, other than farming. Young men were staking their hopes on software courses at fly-by-night colleges, hoping for something better than work at a call center. They all seemed poised to take a leap, but had no idea where they were leaping to.

Many of these people wound up at the rallies of Narendra Modi, the candidate of the Bharatiya Janata Party. The gatherings began like small-town carnivals, as streams of young men in jeans and T-shirts emerged from alleyways and jogged down the road together. Mr. Modi opens his speeches with words of soft affection for his followers, and there were times that his punishing schedule could be seen in his drained face and rumpled clothes, but he gathered strength from the sea of faces tilted up at him, like a battery recharging, and the rallies would finish as a livid, roaring attack on the status quo.

This was not the fight that the Indian National Congress had prepared for, after presiding over a decade of rising incomes. Last fall, when I visited Ajay Maken, one of the party’s senior leaders, in his handsome government-issued British colonial bungalow in New Delhi, he sounded serenely confident about the message that the party would take to voters. It was not a message based on airy promises for the future, he explained, but on concrete things that Congress had already done for “the poorest of the poor.”

Mr. Maken was talking about major pieces of legislation, the most ambitious a food subsidy bill that established a legal right to food for most of India’s population, and could cost the budget as much as $20 billion annually. That bill, pushed through Parliament at the tail end of the Congress-led coalition government’s five-year term, had been seen by many as an electoral juggernaut, guaranteeing the votes of the 148 million people who live below the poverty line.

Why did that not work? One reason is that India’s poor have themselves changed, adopting attitudes and concerns long associated with the middle class. Indians are moving to cities in huge numbers; but even those who remain in villages, surfing the Internet on cheap smartphones, are drawing closer to the way city-dwellers think. Dilapidated infrastructure that they have long tolerated now seems intolerable. They want jobs.

“The Congress remembers us during elections and gives the poor a crutch,” a driver in Varanasi said to one of my colleagues. “But we want to stand on our own feet.”

For generations, Congress politicians have focused heavily on the rural electorate, in part because a 30-year freeze on redistricting kept the number of urban constituencies artificially low, said K.C. Sivaramakrishnan, co-author of “A Handbook of Urbanization in India.”

“There is a certain political attitude which has been there for a long time — that rural is good, rural is simple, rural is plain, rural is beautiful,” Mr. Sivaramakrishnan said, a belief that harks back to Mohandas K. Gandhi, who venerated villages as the ideal expression of human civilization.

But this was an election when we also heard from the cities, places with tawny marble shopping malls, migrant families living under highway overpasses, and armies of tailors, blacksmiths, locksmiths, cobblers, drivers and maids. Urban voters have long been seen as an apathetic group.

But that turned out not to be true at all: Early analysis shows that urban turnout in these elections shot up around 10 percentage points compared with 2009, going from 53 percent to 62 percent. It was even more pronounced in the smaller regional capitals whose populations have exploded in recent years. Turnout in Patna, the capital of Bihar State, increased by nearly 18 percentage points, and in Baroda, a large city in Gujarat, Mr. Modi’s home state, by 22 points, Mr. Sivaramakrishnan said.

The paradox for Congress is that it has lost some of the voters who prospered most during its decade in power. Take Gaurav, the auto-rickshaw driver, who had come to New Delhi from a farming village in Uttarakhand. He acknowledged that he was better off than his father, having acquired a cellphone, a television, and access to good hospitals.

But he was not happy; on the contrary, he was madder and madder. The city’s clogged roads had become such a frustration, Gaurav said, that when he stops in traffic his knuckles go white clenching the handlebar. When he overheard passengers speaking positively about Congress, he would stop his auto-rickshaw, claiming it was broken, and ask them to get out and walk. He was eager, even desperate, for some change that he could not quite explain.

“My wish is to start something so I am not in this precarious situation — earning daily, eating daily,” Gaurav, who uses one name, said. Ahead of state elections in December, he decided to throw his vote behind Arvind Kejriwal, the firebrand leader of the Aam Aadmi Party, which grew out of mass protests against corruption.

In the end, though, it was Mr. Modi who managed to connect with this aspirational India. He did this in part by proudly holding up his own humble origins as the son of a tea vendor — mostly omitting the Hindu nationalist organization that shaped him profoundly — and by heaping disdain on the aristocratic Nehru-Gandhi family and the elites who surround it. He has so widely promoted his achievements in Gujarat, the prosperous and industrialized state he has led since 2001, that people all over India are confidently offering accounts of a place that they have never laid eyes on. While Congress was promising poor voters a series of safety nets, he fed their hopes of rising into prosperity.

The magnitude of those hopes will follow Mr. Modi into office if, as expected, his Bharatiya Janata Party wins a commanding victory on Friday, and they could become a burden.

This month, at a rally in Roorkee, in Uttarakhand, several thousand people had jammed under a red tent, shouting Mr. Modi’s name at the top of their lungs. Shortly before a woman beside him slumped to her seat in a dead faint, Deepak Kumar, 17, was cataloging the changes that he expected to take place when Mr. Modi took office, starting with the end of “atrocities against women.”

“Things which Congress couldn’t do in 10 years, he will do,” Mr. Kumar said happily. “Price rises go on and on and on, but we hope that Mr. Modi will stop it. He will improve education. He will clean the Ganges. There is a lot of dirt in the Ganges.”

“There is a lot of dirt around everywhere,” piped up his companion, 14-year-old Mohit Dhariwal. “He will clean that.” How, I asked, would he manage do all this? Mr. Kumar shrugged; he had no idea. And what if he cannot do it? “This is in the people’s hands,” Mr. Kumar said confidently. “If he does not deliver, he will be kicked out after five years.”