The news that Arizona voters on 5 November had approved the so-called “secure our border” initiative hit Reyna Montoya like a gut punch.

The measure – proposition 314 on the ballot – makes crossing the US-Mexico border without authorization a state crime, empowering local officials to arrest and deport border-crossers and enhancing criminal penalties for unauthorised immigrants who apply for public benefits.

The initiative is modelled after a Texas law that is currently being challenged in court, and some of its key provisions will be blocked until the Texas law, or another similar law, is allowed to take effect.

But when implemented in full, immigrant rights groups fear the measure could bolster Donald Trump’s promise to enact the “largest deportation operation in American history”, and deputise local law enforcement agencies to help him expel as many as 11 million people living in the US.

Montoya, who founded the Phoenix-based non-profit Aliento to support undocumented people and their families, said she has spent the last several days trying to reassure employees, friends and clients, and making sure they know their rights – even as she fears for her own safety.

“My biggest fear is that I’m gonna get rounded up, and put in a detention centre myself,” said Montoya, who was granted a temporary legal permit to remain in the US that she fears the Trump administration will revoke. “This is the reality that I’m living with. That is the reality that undocumented people are waking up to today.”

It’s a familiar fear.

This year’s initiative is strikingly similar to SB1070, a now notorious state measure known as the “show me your papers” law, which 14 years ago made it a crime to be undocumented in the state, deputising law enforcement to demand “papers” from anyone they deemed suspicious.

“It caused so much emotional trauma,” said Montoya, who herself was undocumented when the law was enacted. “There was so much anxiety and uncertainty and stress.”

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Back then, Joe Arpaio, the hardline sheriff of Maricopa county who became known as “the Donald Trump of Arizona” took up a crusade against undocumented immigrants, empowered by SB1070 to stage “round-ups” in Latino neighbourhoods in and around Phoenix. His deputies swept up hundreds of people without evidence of criminal activity.

Montoya, who had been brought into the US as a child without legal authorization, remembers how terrified she felt driving to school each day. “I remember being at each stop sign, and counting very slowly to five ‘Mississippis’ so police officers wouldn’t have any reason to pull me over,” she said. “It took so many survival skills to make it through.”

It wasn’t only immigrants who suffered, Montoya said. As Arpaio he focused on working with the Department of Homeland Security to round up immigrants, violent crimes – including sex crimes – went uninvestigated. Businesses that had long relied on undocumented workers struggled to hire staff, and the state’s hospitality and tourism industry took an additional hit after cities and businesses boycotted Arizona over its harsh policies.

Nearly 15 years ago, the passage of SB1070 was an inflection point in Arizona’s politics. Anger and betrayal over the policy bubbled into a powerful resistance, galvanising a generation of young Latinos and immigrants – Montoya among them – to action. For more than a decade, they fought to tear down the law and vote out its strongest proponents. They protested in the streets, and fought in the courts. They mobilised tens of thousands of voters of colour who helped transform the deep-red state into a political battleground. Many successfully ran for office themselves.

Four years ago, Montoya and her cohort of activists celebrated as Arizona flipped blue – electing a Democrat for president for the first time in 24 years, and electing Democratic majorities to the state legislature for the first time since 1966. Four years before that, the state voted out Arpaio.

“We felt so proud because we did it: we ousted the people who had come after our community,” said Raquel Terán, a former member of the Arizona house of representatives and state senate who started her political career as an organiser against SB1070 and the far-right officials who promoted it.

But a backlash was also beginning to build. Calls for more aggressive immigration enforcement followed national concern over increasing numbers of migrants at the US southern border. Trump and his allies began ratcheting up their xenophobic rhetoric. This summer, the state supreme court rejected a lawsuit filed by immigrant rights groups to remove Proposition 314 from the ballot on constitutional grounds.

Still, the election results hit longtime organisers in Arizona like a blow. “It feels really heavy,” said Terán. “I’m trying to process it as much as I can. But sometimes I also freeze, and I’m like: ‘Oh God, this is all so much.’”

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There is a dissonance, she said, in the fact that in the same election that Arizonans ratified Proposition 314 and elected Trump, who campaigned on a promise of mass deportations and championed the idea that migrants are “poisoning the blood” of our country. Arizonans also chose Ruben Gallego as their senator – bolstering a young, Latino politician who got his own political start alongside Téran and the anti-SB1070 generation.

As in other states, Arizonans’ perceptions of the economy were a driving force in the election. But polls also found that Arizonans of all demographics and political affiliations wanted the government to reform its immigration system and address the rush of migrants at the southern border – they were divided on how to address the crisis.

“I think there has been some sort of disconnect, where people forgot the impact of these laws,” she said. “We need to continue to organise, and continue to help connect the dots of how these policies will impact peoples lives.”

We have to be unafraid, not timid, when it comes to resistance towards the Trump administration

Montoya and others wondered if Republicans’ choice to market Proposition 314 as the “secure our border act” confused voters, who didn’t realise that the law had very little to do with border enforcement and much more to do with policing inside the state. “People maybe didn’t have time to do the research because they are working nine to five jobs and maybe have a second job to make ends meet,” she said. “My hope is that these people will realise how this will impact all Arizonans … and that it’s not too late to speak out.”

Counterintuitively, among those who do remember the impacts of SB1070, and oppose its revival, are small town police and sheriffs in the vast, rural counties along Arizona’s border with Mexico, who they do not have the resources or ability to enforce immigration. The state legislature has not provided any additional funding to the law enforcement who would be deputised with enforcing immigration policy. Some sheriffs have also said it would encourage racial profiling.

David Hathaway, the sheriff of Santa Cruz county, just south of Tucson, said that the law relies on a “racist” mechanism, encouraging officers to stop anyone who looks like a migrant. That could be fruitless, in a county where 40,000 out of 49,000 residents identify as Hispanic or Latino, and 78% speak Spanish at home. “It would be ridiculous for me to go up to practically every single person in my county and say: ‘Let me see your papers, I need to check your immigration status,’” Hathaway told the Guardian in September.

Human rights and immigration groups, including the American Civil Liberties Union, have vowed to continue fighting Proposition 314 and prevent its full implementation.

“Arizona’s original ‘show me your papers’ law was held to be largely unconstitutional by the US supreme court in 2012. Our state has been down this road before with costly litigation,” John Mitchell, an immigrants’ rights attorney for the ACLU of Arizona, said in a statement.

At the same time, advocates are scrambling to prepare to react to the law, and are bracing for more round-ups and ramped-up threats against immigrants as Trump moves to implement his plans for mass deportations. The progressive group Lucha, for example – which knocked on hundreds of thousands of doors ahead of the election urging people to vote for Kamala Harris and against Proposition 314 – has now kicked its immigrant education program into high gear.

“We want to make sure we’re educating the community about what will be coming down the line,” said César Fierros, a communications director at Lucha. The group’s immigrant services department has been urging community members who are eligible to apply for green cards, renew their visas and make sure paperwork is up to date before Trump is sworn into office.

Activists and advocates have also redoubled efforts to share information about legal resources for those fighting deportation, drawing on lessons learned from Trump’s first term, and from the years that Arpaio and SB1070 reigned. When legal manoeuvres stalled or failed, it had become common practice for activists in Phoenix to rally supporters to stage protests against the arrests and deportation of community members. “We have to be unafraid, not timid, when it comes to resistance towards the Trump administration or bad policies like Prop 314,” said Fierros.