Catalonia’s largest left- and right-wing parties agree they want to secede from Spain, but running in the next regional election on a single list is a bridge too far for the Republican Left.

The party’s leader, Oriol Junqueras, said on Tuesday he was in favor of continuing the coalition with regional president Artur Mas’ conservative Convergence and Union but could not support his proposal to contest the election on a single list. “It would be a betrayal of our supporters if we leave the banner of social justice and the fight against corruption in the hands of those who want independence,” he said.

Last month, Mas suggested the region could call early elections to serve as a proxy referendum on independence, provided all separatist parties joined a single electoral list.

Such a move would not only have resolved the ambiguity that resulted from an informal independence vote; it could also have helped Mas’ party stave off an electoral challenge from the less compromising Republican Left.

Catching up with the left

Whereas Convergence and Union has gradually moved in favor of independence, Junqueras’ party has advocated secession from Spain for decades.

A survey published in El Mundo newspaper last week put support for the conservatives at 23.8 percent and support for the Republican Left at 22.1.

Mas previously rejected proposals from the left to interpret a legislative victory for the separatists as tantamount to a vote for independence.

However, last week, he pledged that if independence parties won the next election, the Catalan government would immediately start building up “state-like structures” and be able to secede within a year and a half. Then elections would be called again to set up an independent government.

Junqueras said on Tuesday he favored a constituent process after the next election instead and calling a referendum later to ratify a new constitution.

Central government obstinate

Last month, more than 80 percent of Catalans voted for statehood in what was dubbed a “citizens’ consultation” after Spain’s highest court had struck down a planned referendum as unconstitutional. Roughly half of the region’s 5.4 million eligible voters took part.

Prime Minister Mariano Rajoy ridiculed the vote this weekend, calling it “a farce.” He also pledged to “never negotiate the unity of Spain.”

The central government’s refusal to negotiate increased autonomy with what is Spain’s richest region has fed separatist sentiment. Polls put Catalan support for independence around 45 percent — up from 13 percent as recently as 2005.