The nationalist Convergence and Union (CiU) coalition is set to oust a Socialist-led coalition from power.

ECONOMIST: Spanish politics

Giner told CNN that a victory for Mas and CiU should be considered a certainty.

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Mr Rajoy wants CiU, which is critical of Mr Zapatero's lukewarm reforms, to help him oust the government.

ECONOMIST: Spanish politics

However a pact between CiU - Mr Mas's centre-right nationalist coalition - and Esquerra Republicana will not be easy.

BBC: Catalonia election: Separatists win majority

But local observers point to the large number of undecided voters still swithering between CiU and the left-wing independentistes ERC.

BBC: Catalonia's 'bitter and personal election'

CiU, a party that likes to wield power in Madrid, has enough seats there to offer Mr Zapatero a more stable government.

ECONOMIST: Catalonia is set to have a big role in Spain��s politics

CiU has implemented austerity measures, including controversial cuts to the public sector.

BBC: Catalonia election: Separatists win majority

Whereas both CiU and ERC are split over economic ideology, both agree that Catalonia gets a poor funding deal from the Spanish central government.

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Like its Basque counterpart, however, CiU is likely to be tempted as much by a greater ration of self-government than by another tranche of economic reform.

ECONOMIST: Spanish politics

But Mr Zapatero needs CiU's votes to pass his measures.

ECONOMIST: Spanish politics

Called by president Artur Mas, of the moderate nationalist CiU, after his demands for a new fiscal pact with Madrid were rejected, this election has become both bitter and personal.

BBC: Catalonia's 'bitter and personal election'

Many outside Catalonia are hoping for a CiU victory.

ECONOMIST: Catalonia is set to have a big role in Spain��s politics

CiU is unlikely to win an absolute majority.

ECONOMIST: Catalonia is set to have a big role in Spain��s politics

The Catalan nationalist Convergence and Union coalition, or CiU, the ruling party in the northeastern region of Catalonia, also has seen recent allegations of corruption against current or former leaders, and some of their family members.

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This election will have a profound impact on Spain, as Convergence and Union (CiU), the moderate nationalist party that ran Catalonia for 23 years after 1980, may well return to power, ending a seven-year coalition between Socialists, the far left and extreme separatists.

ECONOMIST: Catalonia is set to have a big role in Spain��s politics