VARANASI, India — Nidhi Tiwari is an upper-caste Hindu. She voted for India’s prime minister, Narendra Modi, in the last election. She lives in Mr. Modi’s constituency, Varanasi, a holy Hindu city. She was, up until last week, one of the millions of bricks in his base.
But Ms. Tiwari, a university student, has turned against Mr. Modi, joining the growing protests sweeping this country after he pushed through a contentious citizenship law that more and more Indians see as anti-Muslim and a blow to India’s foundation of tolerance and secularism.
“I used to see Modi as a strong leader, as the person India had been waiting so long to get,” Ms. Tiwari said. “Now, I see him as a monster.”
Until this outpouring of anger, Mr. Modi seemed unstoppable. Riding a populist wave, he was pushing ahead with plans to bring India closer to becoming a Hindu homeland, a divisive dream harbored by his political party whose roots lie deep in a Hindu-centric worldview that poses an existential threat to India’s large Muslim minority.
Now some of his support is beginning to crack, even in strongholds like Varanasi. For the first time, Indians are standing up to Mr. Modi in a clear, united, widespread and forceful way, saying: No, we don’t want this. How this plays out in the next few weeks could have a seismic impact on India.
The protests are jumping from city to city. They are drawing in an increasingly broad cohort of Indian society, including former Modi fans and many non-Muslims.
If they succeed in slowing him down or changing his course, it could be a lasting victory for a secular India built to honor a dizzying diversity of languages, religions and geographic identities. If the protests fizzle, Mr. Modi’s vision of a Hindu rashtra, or Hindu nation, could draw closer.
“This is undeniably the biggest pushback Modi has faced from civil society since coming to power in 2014,” said Milan Vaishnav, the director of the South Asia Program at the Carnegie Endowment for International Peace.
Varanasi, a city of temples along the banks of the Ganges River that Mr. Modi repeatedly returns to for spiritual strength — and for votes — reflects his challenge. He still has a lot of support, but parts of the city have erupted beneath him, a gauge, perhaps, of the antipathy rising against a prime minister who was once widely hailed as India’s modern-day savior.
Muslims, students, left-leaning professionals, lower- and upper-caste Hindus have poured into the narrow, brick-walled lanes yelling, “Down with Modi!”
The police have responded by beating people up, kicking in doors, shutting down the internet, arresting scores, and in one incident charging into a crowd and setting off a stampede that crushed a 9-year-old boy who was out riding his red bicycle.
As the protests have swelled across the country, hundreds of thousands have joined. Thousands have been arrested and more than 20 killed.
The demonstrations are still mostly confined to the new law that fast-tracks Indian citizenship for migrants from neighboring countries who are Hindu, Buddhist, Christian, Sikh, Parsee or Jain — all of South Asia’s major religions bar one: Islam.
But the broader context is an India whose star is not quite as shiny as it was a few years ago. Grumbles are growing about the weakening economy, which the protests are not helping. Mr. Modi had promised to create millions of new jobs; he has not. Across northern India’s industrial heartland, people are feeling the pinch.
Varanasi may be a sacred city, where countless bodies are cremated along the banks of the Ganges, but it is also a modern industrial city where countless saris are made in factories.
“I’m hearing it all over town: People are fed up with this regime,” said Vishwambhar Nath Mishra, an electrical engineering professor and the head of an important temple. “Why did he push this? Was this really the need of the time?’’
Even at this divisive and turbulent time, much of India is solidly behind Mr. Modi. He has deeper and broader support than any Indian figure has generated in decades, which has enabled him to pursue an agenda that alienates minorities and frightens progressives.
After Mr. Modi’s overwhelming re-election in May, the Hindu nationalist campaign reached a fever pitch. His government stripped statehood from Kashmir, India’s only Muslim majority state, and then passed the new citizenship law.
Mr. Modi’s popularity cannot be chalked up only to the fact that Hindu nationalist ideology plays well in a country that is 80 percent Hindu. The Modi administration has also done a better job than previous governments in pushing big anti-poverty initiatives, such as building 100 million toilets to help stop open defecation and the spread of deadly disease.
His Bharatiya Janata Party and its allies control nearly two-thirds of the lower house of Parliament, a cause and effect of opposition weakness. These past weeks, opposition politicians have shown once again how fractured they are, by not capitalizing on the protests.
There has been nothing close to a coordinated strategy, and as students and intellectuals are dragged away by riot police, many opposition leaders have been cheering on the protesters — from Twitter.
Politically, analysts say, Mr. Modi is safe. But these protests pose a threat to his ideological agenda.
“Modi is not a normal politician who measures his success only by votes,” said Kanchan Chandra, a political scientist at New York University. “He sees himself as the architect of a new India, built on a foundation of technological, cultural, economic and military prowess, and backed by an ideology of Hindu nationalism.”
The effects are already being felt. Mr. Modi’s party lost state elections in Jharkhand this week. And he and party leaders have shelved plans to plow ahead with a national citizenship review.
The process could have forced all Indians to produce documentary proof that they were citizens, difficult in a developing country where countless people do not have such records. The widespread suspicion was that the administration was pushing this review, in combination with the citizenship law, to disenfranchise Muslims, though Mr. Modi has vehemently denied that.
It has been a long time since Mr. Modi, 69, has had to play defense. His career has been an arrow flying straight up, from humble roots and wandering solo through the Himalayas as a young preacher, to becoming a ground-level party operative, then chief minister, then prime minister.
He knows, intimately, the perils of Hindu-Muslim tensions. In 2002, when he was chief minister of Gujarat, he was accused of allowing more than a thousand people, most of them Muslims, to be slaughtered in communal violence. He was never charged, though suspicions remained.
Mr. Modi radiates intensity but lately, he seems a little less self-assured.
At a huge outdoor rally on Sunday afternoon, in the winter chill and in front of a crowd roaring “Modi Modi Modi!” he looked tight, distracted, distant, even a bit angry.
He lashed out at what he called a “conspiracy” by opposition politicians and expressed little sorrow, or even acknowledgment, of those killed. He gave the impression that he welcomed the controversy, thundering, “The more they hate me, the more the love of this country’s public rains on me.’’
Mr. Vaishnav of the Carnegie Endowment said, “This was an incredibly combative speech.”
At the same time, Mr. Modi has been trying to act as if, somehow, everything is normal. He went to a meeting on the Ganges River one day and spoke at an investment conference on another. Within his administration he has expressed confidence that the storm will soon pass. He believes that the discontent is simply naysayers upset about how fast he is moving with policies that previous Indian politicians struggled to carry out.
Though protests have erupted in virtually every Indian state, the violence has been the most intense — and the most people have been killed — in the states controlled by Mr. Modi’s political party, such as Uttar Pradesh.
Witnesses say that police forces under the command of Yogi Adityanath, the state’s chief minister, a Hindu monk and a Modi acolyte, have systematically swept through Muslim neighborhoods, breaking into houses, hauling off Muslim men and destroying Muslim families’ property.
Mr. Adityanath’s police have also been widely accused of firing live ammunition into crowds.
In Varanasi, which is in Uttar Pradesh, the Muslim quarter feels under occupation. Life goes on — children fly kites from rooftops, people fry balls of dough in piping hot skillets, half of the markets are open — but it all happens under a thick tension coiled with violence.
Countless police officers in riot gear and helmets prowl the lanes, submachine guns in hand. The residents glare at them.
“What would I tell Mr. Modi?’’ said Vakil Ahmed, whose son was the one trampled last week. “I’d ask: Why are you doing these atrocities to us?’’
Over the next few weeks, protests will most likely continue, though with year-end vacations starting now, many students will disperse to their hometowns, cooling the universities down.
To get tens of millions on the streets, other groups will have to join. The likeliest would be Dalits and members of other lower castes, who have been complaining for years about discrimination under Mr. Modi. Some Dalit leaders have attended protests but this has yet to catalyze a wave.
For now, many protesters have been young progressives like Ms. Tiwari, a 20-year-old political science student whose family are longtime Modi supporters.
“Every day I argue with my dad,” she said.
And even though he will not give her logical arguments, she says, he still supports Mr. Modi.