Montserrat Aguilera wasn't intending to vote for the Catalonia region to secede from the rest of Spain.

But the 52-year-old laboratory worker changed her mind amid an unprecedented crackdown by Spain's government as it tries to prevent Sunday's independence referendum from going ahead.

Spain and its most powerful and prosperous region are headed for a showdown, with police trying to shut down polling stations to stop the referendum and activists, students and parents occupying schools designated voting places to keep them open.

Much remains unclear, including whether police will forcibly remove people who are still in the polling stations at a 6 a.m. Sunday deadline and how many of Catalonia's voters will be able to cast ballots amid the central government's crackdown.

Also unknown is what happens next if regional leaders declare any vote legitimate and Catalonia declares independence. The referendum was suspended under constitutional rules weeks ago so a court could consider its legality.

Turnout will be key, and if people like Aguilera are any indication, it could be high. She wanted a referendum to be held under constitutional rules so she could vote "no" and try to keep Spain and Catalonia united. Now, she wants Madrid to feel the pinch of the region's disgust.

"I don't agree with the way the vote has been convoked by the Catalan government. It should have been a legal one," Aguilera said. "But this is going to be a demonstration of democratic force to show (Prime Minister Mariano) Rajoy that we deserve respect and that he needs to listen to Catalonia."

Catalan authorities have pledged to make the voting possible even if police, acting on judges' orders, manage to close polling stations and seal off ballot boxes. Some 5.3 million people are eligible to vote in the region, one of 17 in Spain.

The latest surge for independence essentially started in 2010, when Spain's Constitutional Court struck down key parts of a groundbreaking charter that would have granted Catalonia greater autonomy and recognized it as a nation within Spain.

The rejection stung, and Spain's 2008-2013 financial crisis and the harsh austerity measures that followed generated more support for secession, with many Catalans feeling they could do better on their own. Catalonia contributes a fifth of the country's 1.1 trillion-euro economy ($1.32 trillion.)

While the vast majority of Catalans favor holding a referendum, they have long been almost evenly split over independence.

If "yes" wins, Catalan authorities have promised to declare independence within 48 hours. No minimum participation rate has been set, but regional President Carles Puigdemont has acknowledged that a significant turnout will be needed to declare the results legitimate.

In a mock referendum in 2014, only about 35 percent of Catalans voted. Eighty percent favored independence.

Officials say the Spanish crackdown could make the difference this time. Catalan Vice President Oriol Junqueras said six out of 10 Catalans were expected to vote, according to the regional government's polling.

Nou Barris, where Aguilera lives, showed the least support among Barcelona's neighborhoods for separatist parties in regional elections two years ago. In balconies and windows, there are few of the pro-independence flags ubiquitous in other central and wealthier areas of Barcelona.

Still, Aguilera says many in her neighborhood, including her son, have decided to show for Sunday's disputed vote.

"Vote yes, vote no, vote null or an empty ballot, but vote to be free and be heard," she said. "These two governments need to sit down and talk, and this is how we'll make them understand that."

The Spanish government says the vote, which has been ordered suspended by the Constitutional Court, will not take place. It has called in thousands of police reinforcements that are being housed in ferries in Barcelona's port, raising tensions in one of Europe's most popular tourist destinations.

The government has also initiated a barrage of legal challenges, including placing 700 pro-independence mayors under investigation and briefly arresting a dozen or so government officials.

"These are not easy days, for sure, but we feel strong," Puigdemont said recently. "While Spain acts like a regime where the authority of power grows inversely to its moral strength, we feel increasingly supported by the Catalan people's greatest asset: its people."

But it's hard to see how a vote will take place when millions of ballot papers were seized and police have been ordered to make sure no polling center stays open. There is no electoral board to monitor the election, but Catalan authorities say votes will be counted.

"Voting is not guaranteed," Andrew Dowling, a Catalonia specialist at Cardiff University in Wales, said. "We don't know what will happen but there won't be a referendum in any meaningful sense."

There has also been little or no campaigning by those opposed to independence.

"The 'no' side don't feel they have to turn out on Sunday because they don't think independence is going to happen," Dowling said.

No country or international body has expressed an appetite for Catalan independence either. The European Union backs Spain and says an independent Catalonia would have to reapply for EU membership, something Spain could block.

"On a legal level, Madrid is right," European Parliament President Antonio Tajani said Friday. "I think it's important to talk on a political level after Monday and to respect laws — Catalan laws and Spanish laws."

U.S. President Donald Trump said Tuesday that Spain should stay united, branding the secession move as "foolish."

Rajoy, the prime minister, has warned Catalonia to drop the referendum bid, which he called a "totalitarian act."

Talks between the two sides have been virtually nonexistent and both accuse each other of acting illegally and undemocratically.

The issue has so far had almost no economic fallout, although the S&P credit rating agency warned that growth prospects may weaken if tensions in Catalonia escalate.

"If you have got financial interests in Madrid or internationally you do not think that Catalan independence is imminent and I think that feeling is true for lots of Spanish people and lots of Catalans," Dowling said.


Giles contributed from Madrid.


Find complete AP coverage of the Catalonia referendum here.