(CNN) Under Prime Minister Narendra Modi , the Indian government has stripped the country's only Muslim-majority state of autonomy and rolled out a citizenship check in the northeastern state of Assam that effectively left nearly 2 million people stateless, many of them Muslims.

And when Modi backed the passage of a controversial new citizenship law , which prioritizes immigrants from three Muslim-majority countries of virtually every religious stripe over Islam, protests broke out across India.

The Prime Minister, whose Bharatiya Janata Party (BJP) was re-elected in a landslide victory earlier this year, has dominated Indian politics since first sweeping to power in 2014. While he has been hailed for his efforts to bring prosperity to poorer regions and root out corruption, his emphasis on empowering India's Hindu majorityhas raised concerns among its Muslim minority

To Modi's critics, the Citizenship Amendment Act (CAA) -- which fast-tracks applications for immigrants, including Hindus, Sikhs, Buddhists, Jains, Parsis and Christians who arrived in India before 2015 -- has become the most brazen example of a Hindu nationalist agenda aimed at marginalizing Indian Muslims. Opponents say it is part of an effort to tear at the fabric of India's secular identity.

Since the law passed through both houses of Parliament last week, demonstrations have swept university campuses in at least nine states. Protesters have taken to the streets across Assam and Tripura over fears that large numbers of Hindus, who migrated to the region in the past few decades, will now be able to get their citizenship fast-tracked. Many there fear it will dramatically recast the religious and ethnic makeup of the northeastern states -- home to 200 distinct indigenous groups.

"In the north, they believe the bill has gone too far and the amnesty will allow too much immigration," Milan Vaishnav, director and senior fellow of the South Asia Program in the Carnegie Endowment for International Peace, told CNN.

The new law will make it more difficult for Muslim migrants to get Indian citizenship. And critics are worried it might pave the way for nationwide citizenship tests, stripping the rights of Muslims who have lived in India for generations but cannot prove their family's lineage -- turning countless people stateless.

Home Minister Amit Shah has repeatedly said that the government will roll out a national citizenship registry.

Modi tried to reassure the public on Monday, saying on Twitter that the new law "does not affect any citizen of India of any religion." And that "no Indian has anything to worry" about.

But when a citizenship registry took place in Assam earlier this year it left 1.9 million people off a list of Indian citizens. The government said at the time that no one would be declared a foreigner if they are not on the list, but that failed to temper concerns.

What is at stake is "the future of liberal democracy in India," Vaishnav said. "And it looks like a side, which has been asleep or at least silent, has really woken up and made sure that their voices are being heard."

Photos: Protesters rally against India's citizenship bill An Indian Muslim participates in a protest against a new citizenship law that opponents say threatens India's secular identity, in Mumbai, India, on Friday, January 24. Hide Caption 1 of 33 Photos: Protesters rally against India's citizenship bill A Muslim youth waves the Indian flag during a protest held by the Muslim community in Bangalore on January 24. Hide Caption 2 of 33 Photos: Protesters rally against India's citizenship bill A heart made of paper boats with slogans on them rests near a protest in the Shaheen Bagh neighborhood in New Delhi on Wednesday, January 16. Hide Caption 3 of 33 Photos: Protesters rally against India's citizenship bill Protesters light candles near posters of Mahatma Gandhi and politician and social reformer Bhimrao Ramji Ambedkar during a demonstration against India's new citizenship law at Mansoor Ali Park in Allahabad on Tuesday, January 14. Hide Caption 4 of 33 Photos: Protesters rally against India's citizenship bill Police personnel try to protect a man attending a protest against graffiti on the shutters and walls of Church Street condemning Indian Prime Minister Narendra Modi and India's new citizenship law in Bangalore on Tuesday, January 14. Hide Caption 5 of 33 Photos: Protesters rally against India's citizenship bill Activists of All Assam Students' Union and other indigenous organizations participate in a torch procession against the Citizenship Amendment Act in Guwahati, India, on Saturday, January 11. Hide Caption 6 of 33 Photos: Protesters rally against India's citizenship bill Protestors shout slogans outside the Delhi Police Headquarters following clashes between student groups at Jawaharlal Nehru University in New Delhi on Sunday, January 5. The violence injured around 34 people, according to police. Hide Caption 7 of 33 Photos: Protesters rally against India's citizenship bill Placards lie next to Indian Muslims offering prayers during a protest on Saturday, January 4. Hide Caption 8 of 33 Photos: Protesters rally against India's citizenship bill Policewomen detain a student protesting outside Uttar Pradesh Bhawan in New Delhi on Friday, December 27. Hide Caption 9 of 33 Photos: Protesters rally against India's citizenship bill Demonstrators gather at the Quddus Saheb Eidgah grounds to take part in a rally against India's new citizenship law in Bangalore on Monday, December 23. Hide Caption 10 of 33 Photos: Protesters rally against India's citizenship bill Demonstrators sit next to bonfires during dusk as they block a road during a protest in New Delhi on Sunday, December 22. Hide Caption 11 of 33 Photos: Protesters rally against India's citizenship bill Protesters gather by the Jama Masjid mosque in New Delhi to demonstrate against India's new citizenship law on Friday, December 20. Hide Caption 12 of 33 Photos: Protesters rally against India's citizenship bill Policemen with batons charge a protester in Ahmedabad on Thursday, December 19. Hide Caption 13 of 33 Photos: Protesters rally against India's citizenship bill Indians gather during a protest rally in Mumbai on December 19. Hide Caption 14 of 33 Photos: Protesters rally against India's citizenship bill An officer flees a police station damaged by protesters during a demonstration in Lucknow on December 19. Hide Caption 15 of 33 Photos: Protesters rally against India's citizenship bill Chief minister of West Bengal state and leader of the Trinamool Congress Mamata Banerjee, along with party supporters, walks in a mass rally across Howrah bridge in Kolkata on December 18. Hide Caption 16 of 33 Photos: Protesters rally against India's citizenship bill Students from Jamia Millia Islamia, a university in New Delhi, shout slogans during a protest on Tuesday, December 17. Hide Caption 17 of 33 Photos: Protesters rally against India's citizenship bill People standing on roofs in New Delhi watch police gathered next to a demonstration on December 17. Hide Caption 18 of 33 Photos: Protesters rally against India's citizenship bill Students and activists protest outside the Allahabad University campus in Allahabad, India, on Monday, December 16. Hide Caption 19 of 33 Photos: Protesters rally against India's citizenship bill People participate in a mass rally in Kolkata, India, on December 16. Hide Caption 20 of 33 Photos: Protesters rally against India's citizenship bill Demonstrators hold signs at the University of Mumbai. Hide Caption 21 of 33 Photos: Protesters rally against India's citizenship bill A bus is seen on fire following a demonstration in New Delhi on Sunday, December 15. Hide Caption 22 of 33 Photos: Protesters rally against India's citizenship bill A child prays during a condolence event in Guwahati, India, for demonstrators killed in anti-CAB protests. Hide Caption 23 of 33 Photos: Protesters rally against India's citizenship bill Demonstrators shout slogans during a protest in Guwahati on Friday, December 13. Hide Caption 24 of 33 Photos: Protesters rally against India's citizenship bill Relatives of Sam Stafford, 18, who was killed during clashes with police the previous day, react in Guwahati on December 13. Hide Caption 25 of 33 Photos: Protesters rally against India's citizenship bill Indian Muslims demonstrate against the bill in New Delhi on December 13. Hide Caption 26 of 33 Photos: Protesters rally against India's citizenship bill Police fire tear gas during a protest in Guwahati on Thursday, December 12. Hide Caption 27 of 33 Photos: Protesters rally against India's citizenship bill Indian soldiers patrol near a burnt vehicle during a curfew in Guwahati on December 12. Hide Caption 28 of 33 Photos: Protesters rally against India's citizenship bill An Indian police officer aims his gun before firing toward protesters who threw stones in Guwahati on December 12. Hide Caption 29 of 33 Photos: Protesters rally against India's citizenship bill Indian youth congress members hold torches as they demonstrate in New Delhi on Wednesday, December 11. Hide Caption 30 of 33 Photos: Protesters rally against India's citizenship bill Security personnel use batons to disperse students protesting against CAB in Guwahati on December 11. Hide Caption 31 of 33 Photos: Protesters rally against India's citizenship bill Protesters on motorbikes hold placards during a protest against the bill in Guwahati on Tuesday, December 10. Hide Caption 32 of 33 Photos: Protesters rally against India's citizenship bill Demonstrators shout slogans during a shutdown called by the North East Students' Organization in Agartala, India, on December 10. It was hours after lawmakers approved the government's new citizenship bill. Hide Caption 33 of 33

The backlash

The protests are sure to have caught Modi -- who has developed a reputation for being a Teflon premier -- somewhat off guard. The leader has enjoyed widespread support, even when his public initiatives have hurt citizens -- and the economy.

Modi's BJP has doubled down on what critics call the party's nationalist agenda, Buoyed by a strong grip on power and a faithful Hindu base,Modi's BJP has doubled down on what critics call the party's nationalist agenda, known as Hindutva

Critics are worried the party is using its stronger mandate to redefine India -- home to the world's second largest Muslim population -- as a religious state and a Hindu homeland.

Progressive Indians watched in horror as Modi stripped Jammu and Kashmir -- India's only Muslim-majority state -- of its partial autonomy in August. Yet "very few people stormed the streets," Vaishnav said.

This, in part, may explain why the government failed to anticipate the potential backlash to the citizenship bill. As protests roiled the country over the weekend, the government shut down the internet in several affected states in a bid to maintain law and order.

"The BJP have been adept at using their grassroots presence to build support for their policies and have been effective at sidelining institutions such as parts of the media," Champa Patel, head of the Asia-Pacific program at the UK-based Chatham House think tank, told CNN.

But they "have been backfooted by the scale of resistance to (the law)," Patel said. "The question now is how will they respond because it's the first real test that they have faced."

Protests broke out at university campuses in at least nine states against the BJP's nationalist agenda.

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India's government says the law is a humanitarian measure to help persecuted religious minorities from its three neighbouring countries -- Pakistan, Bangladesh and Afghanistan.

And as protests continued in the capital New Delhi on Tuesday, Modi accused political rivals of fomenting dissent and encouraging the discontent.

Meenakshi Ganguly, the South Asia Director of Human Rights Watch, told CNN that the government needs to "understand that a Hindu majoritarian ideology may not be acceptable to a large number of Indian citizens." That is a view shared by more than 500 jurists, lawyers, academics and actors, who have condemned the legislation in a statement seen by Indian media.

But in spite of mounting grievances, analysts think it is unlikely that the BJP will scrap the law. "Modi still remains, head and shoulders, the most popular politician in India," Vaishnav said.

The BJP has a wide mandate since their second consecutive win in the general election, a race fought on a cultural agenda that appealed to their hard-line base. "And I don't think they are going to deviate from it," Vaishnav added.

In the meantime, India lacks a foreplan for what comes next. Its detention centers do not have the capacity needed to house "millions of people that could potentially be caught up," if a nationwide citizenship check is rolled out, Vaishnav said.

And there appears to be no existing talks with neighboring countries, like Bangladesh, on the issue of deportation, Patel, from Chatham House, added.

As concerns mount, India watchers say Western governments have taken too soft a touch with the country -- widely seen as a potential democratic counterpoint to neighboring China.

"I think what that does is turn a blind eye to just how authoritarian the BJP has been within India," Patel said.

The foreign community "is waiting and watching to see how the (law) will be implemented," Vaishnav added.

"Are you going to see large numbers of Muslims detained or lose their citizenship? It is a game of wait and see."