Pro independence demonstrators march waving esteladas or independence flags, during a demonstration supporting the imprisoned pro-independence political leaders in Barcelona, Spain, Saturday, Feb. 16, 2019. Thousands of Catalan separatists are marching in Barcelona to proclaim the innocence of 12 of their leaders who are on trial for their role in a failed 2017 secession bid. (AP Photo/Emilio Morenatti)

Pro independence demonstrators march waving esteladas or independence flags, during a demonstration supporting the imprisoned pro-independence political leaders in Barcelona, Spain, Saturday, Feb. 16, 2019. Thousands of Catalan separatists are marching in Barcelona to proclaim the innocence of 12 of their leaders who are on trial for their role in a failed 2017 secession bid. (AP Photo/Emilio Morenatti)

BARCELONA, Spain (AP) — The secession crisis festering in Spain’s northeastern corner of Catalonia has spread to the political heart of the European Union nation.

Twice in less than a year, separatist lawmakers from Catalonia have played the role of king slayer, with their votes in the national Parliament in Madrid proving the decisive push to topple consecutive governments.

Catalan separatists momentarily aligned with their political nemeses this week by joining Spain’s right-wing parties to kill the Socialist government’s spending bill, after talks between the government and the separatists collapsed over the possibility of a referendum on secession.

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The failure to pass a national spending bill led Prime Minister Pedro Sanchez on Friday to call an early election for April 28.

This latest blow to Spain’s political stability came eight months after the same separatist Catalan lawmakers backed the Socialists in a no-confidence vote to oust the then conservative government of the Popular Party.

“We made Pedro Sanchez prime minister as a result of the no-confidence vote for the exact same reasons that we have had to maintain our position (against) his budget bill,” said Eduard Pujol, a leading member in Catalonia’s regional legislature. “You cannot govern Spain without listening to Catalonia.”

Separatists forces showed their strength on Saturday when tens of thousands rallied in Barcelona to demand a non-guilty verdict for 12 of their leaders, who are on trial in Spain’s Supreme Court for their roles in a failed secession attempt in 2017. Barcelona’s police calculated that 200,000 people joined the march.

The front line of marchers held a long banner saying in Catalan “self-determination is not a crime.”

While they claim that Catalonia has a right to self-determination, Spain’s government says any vote on independence would require the national Parliament to amend the Constitution.

Polls point to a fragmented political spectrum that will leave a future Spanish government in need of cobbling together partners for a coalition government.

That means Catalonia’s separatists could still hold leverage, especially if Sanchez’s Socialists need their votes to stay in power.

“Spain will be ungovernable as long as it doesn’t confront the Catalan problem,” said Catalonia’s regional government spokeswoman, Elsa Artadi.

But forcing a new election is risky. Spain’s conservative and far-right parties — the Popular Party, the center-right Citizens party, and the far-right Vox party — will all focus their campaigns on taking a hard line against the separatists.

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The anti-Catalonia formula worked for the right-wing parties in a regional election in December when they managed to end the Socialists’ 36 years in power in Spain’s south.

Currently a little less than 50 percent of the voters in Catalonia support parties whose goal is independence. But few doubt that a crackdown from Madrid would push more Catalans into the separatist camp.

The decision to withdraw their backing from Sanchez, however, was divisive within the separatist bloc. Joan Tarda, a national parliament member and moderate separatist, lamented that Sanchez had called an election instead of trying to maintain talks with the separatists.

″(Sanchez) has decided to take a gamble with a situation that can become even more difficult than it already is,” Tarda said. “If things go our way, what will the scenario be? We will be right back where we were last week with the need to negotiate.”