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Pain in Spain as Catalonia gears up for key vote

Spain's prosperous north-eastern region of Catalonia has long been a thorn in the side of the country's national government with its centuries-long struggle for independence. This weekend the wound could get deeper if separatists win a regional election and move towards going it alone.

Catalonia has a distinct identity, language and traditions from the rest of Spain and its political parties and politicians, including the current Catalan President Artus Mas, have long-argued for the wealthy region to separate from its poorer Iberian parent.

Now, with a regional election on Sunday, the main pro-independence parties – the Democratic Convergence of Catalonia and Republican Left of Catalonia, and several smaller parties -- have united to give their cause greater strength and give Spain a bigger headache.

People at a Catalan Pro-Independence demonstration celebrating the Catalan National Day on September 11, 2015.
David Ramos/Getty Images

If they win a majority of seats in the 135-seat Catalan parliament based in Barcelona, they have vowed to set up an independent state within 18 months. Indeed, the election has been portrayed widely as a referendum on succession although Spain has ruled out any such notion.

What the polls say

Three polls for Spanish newspapers El Pais, La Vanguardia and ABC show the main pro-independence movement Junts pel Si (JxSi, or the "Together for Yes" coalition) winning between 63 and 67 seats, or around 41 percent of the vote, Reuters reported, just shy of an absolute parliamentary majority of 68 seats.

Catalonia is an important part of Spain's economic and political life, making it worth fighting for. It is a major contributor to the Spanish economy with nearly 19 percent of Spain's gross domestic product (GDP), according to research by the Organization for Economic Co-operation and Development (OECD).

If it succeeds in becoming independent, not only could Spain lose a substantial financial contribution, it could encourage another region fraught with separatist sentiment – which in the past manifested itself in bombing campaigns -- in the autonomous Basque country to bid for full independence.

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Voter turnout could be decisive for pro-independence parties, according to Antonio Barroso, senior vice president of risk consultancy Teneo Intelligence.

In a note Tuesday, Barroso said that if Mas is re-elected, the pro-independence movement will gain momentum but only if the awkward coalition of pro-independence parties overcome their differences.

"Although Mas' re-election will test the unity of the secessionist movement, pro-independence parties will make symbolic moves towards a Catalan state if they obtain a majority, prolonging the stalemate with the central government," he said.

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He believed that the coalition would tread carefully, adopting "incremental steps" towards independence with the idea being to keep the Catalan political momentum alive without taking it to a breaking point with the Spanish central government."

Strategists at Rabobank appeared more relaxed about the possibility of the separatist coalition succeeding, however, saying in a note Wednesday that the main parties "are from the opposite ends of the political spectrum (the right and left respectively) with their only common ground being a call for independence. Thus the thinking is that they will struggle to govern effectively together."

Madrid worried

The election will be watched closely in Madrid, although the government might take heart from the failure of an independence referendum in Scotland last year, in which, unexpectedly, only 45 percent of Scots voted to leave the U.K.

What's more, Catalonian independence is illegal under the existing Spanish constitution, making it more likely that pro-independence parties will try a gentler approach – like devolved Scotland – to gain more powers from the Spanish government

"This is unlikely to change any time soon given it is probable that three of the four largest parties that will emerge from the 2015 Spanish national elections are pro-union. (The main pro-independence parties) are therefore likely to focus on the more realistic aim of greater devolution of power," Rabobank's strategists said.

- By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt. Follow us on Twitter: @CNBCWorld