BARCELONA — Voters in Spain's wealthy Catalonia region Sunday sliced the majority held by a nationalist alliance in snap elections, giving strong gains to left-wing parties that favor independence, exit polls said.
Artur Mas, the center-right leader of the regional government, had promised to hold a referendum on self-determination within four years if the vote for the 135-seat parliament gave him a mandate — a move which the leftist parties would also support.
Early results showed that Mr. Mas' nationalist alliance won between 54 and 57 seats, down from 62 currently, as leftist parties nearly doubled their share to as many as 38 seats, according to Catalan television channel TV3.
The result weakened the presence of Mr. Mas' alliance in the parliament, but the strong showing of the pro-independence parties could lend weight to calls for a referendum from Spain at a time of deep financial crisis.
Mr. Mas called early elections as part of a power struggle with the central government in Madrid run by Prime Minister Mariano Rajoy centered on the size of Catalonia's contribution to national coffers.
What began as a quarrel over money turned into a test over Spain's territorial integrity.
"These are the most decisive and transcendental elections in the history of Catalonia," Mr. Mas said after voting in Barcelona. "There is much at stake for all 7 million of us Catalans."
Polls forecast the majority of seats would be won by parties supporting a referendum on independence, a plebiscite that Spain's central government has ridiculed and called "unconstitutional."
According to Mr. Rajoy, only the central government has the constitutional right to call a referendum, and then it would almost certainly have to include the whole of Spain.
Mr. Rajoy has said that talk of independence is a side issue to the country's real problem, which is to find a way to create employment and address its deficit.
While Mr. Rajoy is immersed in combating Spain's worst financial crisis in decades, Mr. Mas claims Catalonia is being asked to shoulder too much of the tax burden and that it could do better if it separated and tried to become an independent member state of the European Union.
"Five years ago, I was in favor of a federal model with Spain, but now we have seen that is not viable," said Miquel Angel Aragon, a 37-year-old aid worker. "I am in favor of independence."
Catalonia is responsible for about a fifth of Spain's economic output, and many residents feel central government gives back too little in recognition of the region's contribution.
Catalans have said in growing public protests that their industrialized region is being hit harder than most by austerity measures aimed at avoiding a national bailout like those needed by Greece, Ireland, Portugal and Cyprus.
Madrid traditionally has said that simplifying the state's financial model by excluding overall costs such as defense only creates a distorted image of how taxation and spending are distributed.
A rising tide of Catalan separatist sentiment was spurred when Mr. Rajoy rejected Mr. Mas' proposals to lighten Catalonia's tax load. More than 1.5 million people turned out Sept. 11 for the largest nationalist rally since the 1970s in Barcelona.
These growing economic concerns have combined with a long-standing nationalist streak in Catalonia, which has its own language and cultural traditions that were harshly repressed by the military dictatorship of Francisco Franco from the end of Spain's Civil War in 1939 to Franco's death in 1975.