* Polls show most Catalans back pro-independence parties
* Secessionist threat a major problem for Rajoy
* Catalans blame Madrid for region's debt problems
* Catalans feel their taxes are propping up poorer regions
By Fiona Ortiz
BARCELONA, Spain, Nov 20 (Reuters) - Spain's wealthy but financially troubled region of Catalonia chooses a new government on Sunday in an election that could trigger a constitutional crisis over a resurgent Catalan breakaway movement.
Opinion polls show most Catalans will vote for pro-independence parties, either from the left or right, handing their leader a mandate to hold a referendum on secession, despite strong resistance from the Spanish government.
The secessionist threat is a major problem for Prime Minister Mariano Rajoy who is trying to show stability and fiscal responsibility in his fight to keep Spain in the euro currency zone and avoid an international bailout, despite a savage recession.
Catalan President Artur Mas is expected to win re-election in voting for the regional assembly in Barcelona, after he converted to the independence cause following a massive pro-secession march in September.
"I hope to be the last president of a Catalonia that the Spanish state is trying to destroy through a dirty campaign," Mas, who leads the conservative Convergence and Union Party (CiU), declared last weekend.
"The next one will not depend on the Spanish state and they will no longer be able to destroy it," he told a campaign rally. Supporters chanted "independence, independence" back to Mas, who promises to call a referendum on statehood within four years.
Like the Basque Country, which also borders France, Catalonia has its own language and sees itself as different from the rest of Spain.
Catalonia's busy Mediterranean ports, car factories, chemical plants and banks account for a fifth of Spain's economy. Until recently the region of 7.5 million people was content to push for greater self-governance - such as collecting and spending its own taxes - without seeking independence.
But Spain's recession, with 25 percent unemployment and drastic public spending cuts, has sharpened a Catalan perception that they are taxed unfairly.
Like the rest of Spain, Catalonia overspent during a decade-long property boom that crashed in 2007 and now it cannot borrow on the markets on its own because its debt has been downgraded to junk. That forced Mas, who as head of the regional government is elected by the assembly rather than directly by voters, to ask Madrid for a 5 billion euro bailout to meet debt payments.
Even so, Catalans blame their problems on Madrid rather than their own leader. Just as Germany has wearied of bailing out Greece and other southern European countries, many Catalans feel their taxes are being used by Madrid to prop up poorer areas of the country.
"Madrid is playing with us," said 33-year-old David Box, a construction worker who supports Mas and independence.
Box sat on a bench on the iconic La Rambla boulevard in the Catalan capital of Barcelona, Spain's second city. Around him the city's famous modernist architecture buildings flew the pro-independence flag - a lone star against yellow and red stripes.
In part inspired by independence drives in Scotland and Belgium's Flanders, a growing number of Catalans believe their region - which has more people than Denmark and an economy rivaling Portugal's in size - would be better off on its own.
Polls show that between 46 percent and 57 percent of Catalans want their own country, the highest levels ever.
"We have turned a regular election into a referendum," said Alfred Bosch, of leftist independence party Esquerra Republicana (ERC), which is projected to win 18 seats and almost double its presence in the 135-seat assembly.
ONE-WAY TICKET TO NOWHERE
Secessionist fever in the native region of surrealist artist Salvador Dali alarms the rest of Spain, and not only because the world-champion national soccer team fields many Catalan players.
Prime Minister Rajoy warns that Catalonia would have to re-apply to join the European Union, a lengthy process, while King Juan Carlos has also called for unity.
At a weekend campaign rally for his People's Party candidate in Catalonia, Rajoy cautioned voters "not to buy a one-way ticket to nowhere."
Pro-independence Catalans argue that a strong referendum majority for independence would force Spain to change the constitution and the EU would have to respect self-determination.
Catalonia would probably gain no early official representation at the European Central Bank if it split away from Spain, although it could keep using the euro currency. Economists say that in the short term, a divorce from Madrid would cause enormous economic damage.
Separatism in Catalonia and the Basque Country was largely suppressed under the 1939-1975 dictatorship of General Francisco Franco. When Spain returned to democracy a new constitution gave the country's 17 regions significant self-governing powers.
Enthusiastic about their new autonomy Catalans established their own police force, opened delegations abroad and revived their language. The independence movement died down in the 1980s and '90s as people embraced a dual identity as Catalans and Spanish.
But the mood has shifted again. Catalans were outraged two years ago when the Constitutional Court struck down some aspects of their autonomy. This year Rajoy refused to negotiate with Mas over allowing Catalonia to keep more of its taxes.
The frustration crystallised in the biggest-ever demonstration for independence on Sept. 11, Catalan national day, when hundreds of thousands marched in the streets.
Days later, Mas, a 56-year-old economist who has led Catalonia for three years, abandoned the pursuit of greater autonomy through negotiations with Madrid. He said Catalonia needed statehood and called an early vote to test support for the idea.
The sudden intensification caught many people by surprise.
"Everything sped up very quickly. The people got ahead of the politicians. Mas had to recognise the citizens' demands," said Marti Estruch, press officer for the Generalitat, as the Catalan government is known.
Polls show Mas's CiU winning about 62 seats on Sunday. It's not enough for an absolute majority, but together with other parties such as the ERC, independence supporters will probably have a two-thirds majority in the Catalan parliament.
Some Catalans say they will vote for CiU to send a message to Madrid and Europe. "I don't like how Spain treats us. I am thinking of voting for CiU to support the movement," said Ofelia Sala, a 52-year-old social worker who usually votes for a leftist party.
Some voters denounce Mas as an opportunist who will soon renew talks with Madrid over taxes, while others suspect his newly-found independence fervour is meant to distract them from spending cuts in hospitals and schools.
"Independence won't help us resolve all the issues we have," said Inma Prat, 69, a retired nurse who speaks Spanish with a strong Catalan accent.
A Catalan business executive, who asked not to be named, said the region's biggest companies are keeping their views on secession quiet. Support for independence could anger customers elsewhere in Spain, while voicing opposition could hurt their business in Catalonia.
But smaller companies believe a new, independent, tax structure will allow the region to invest more in infrastructure, which would be good for business.
They say Catalans are cheated out of 16 billion euros in tax revenue a year by the current system, under which the regions collect taxes and turn them over to Madrid, which transfers money back using a complex formula.
Pimec, a Catalan business chamber of 105,000 small- and medium-sized companies, found clear support for independence in an on-line poll of several thousands of its members.
Josep Gonzalez, president of Pimec said Madrid has failed Catalonia. "If you have an economic driver, keep giving it fuel, they should be taking care of us."