For the third time in four years Spaniards head to polling stations Sunday, and are likely to confirm a Europe-wide electoral pattern of voters moving away from traditional parties.

With the emergence of new populist-based factions, European politics is becoming more fragmented, leading to minority governments, misshapen governing coalitions, more political deadlock and less predictability. That is likely to be the fate of Spain come Sunday, with some analysts forecasting another snap election may have to be called later in the year.

The election will confirm the fragmentation of politics, according to Ivan Llamazares, a political scientist at Universidad de Salamanca. He says it will “be very difficult to form stable legislative majorities in the coming years” in Spain thanks to a breakdown in centrist, consensual politics.

The Socialists, led by Pedro Sanchez, the current prime minister, are expected to attract the largest share of the vote in an ill-natured general election on April 28, which has seen tempers fray and accusations of treason being hurled with abandon. The rise of the ultra-nationalist Vox party, which last December won 12 seats in the regional parliament in Andalusia, has added a sharpness and volatility to the election.

Socialists more united under Sanchez

Coming out on top of the polls Sunday will be a remarkable achievement in itself for Sanchez — until last year the Socialists were mired in vicious splits and appeared out for the count following two bruising electoral defeats. Pollsters suggest Sanchez’s party will secure 30 percent of the vote.

But, despite their revival, the Spanish Socialist Party (PSOE) will likely be denied an overall majority. It will be best positioned, though, to try to form a formal coalition government, the first at the national level since the restoration of democracy in 1977, predict pollsters and analysts.

Sanchez began the Socialist comeback last May when he seized on a string of corruption scandals to unseat the Conservative government of Mariano Rajoy with a surprise no-confidence motion that attracted the support of lawmakers in the the leftist Podemos party as well as Catalan and Basque nationalists.

Since then as the prime minister of a minority government, Sanchez has been astute in rebuilding the PSOE’s base with a series of progressive actions. They have included hiking the minimum wage, appointing a female-dominated Cabinet and starting the legal process to move the embalmed body of the late military dictator, Gen. Francisco Franco, from a huge mausoleum near Madrid, which has become a shrine for far-right activists.

Those moves have helped the PSOE shoot ahead in the opinion polls of the Conservative Popular Party (PP). Until 2015, the PSOE and the PP alternated in power, sometimes relying on Catalan or Basque nationalists to make up the numbers to secure a working parliamentary majority. But with newer populist-based parties vying for votes, including the right-of-center Ciudadanos, leftist Podemos as well as the far-right Vox, the ease of what was in essence a two-party political system has long disappeared.

Vox party: ‘Make Spain great again’

One factor that has helped Sanchez the most, according to Anna Rosenberg, a global investment adviser, has been the emergence of Vox, which promises “to make Spain great again” and crack down on immigration. “People are really scared of the rise of the right-wing parties and that will mobilize voters that might not have been expected to vote before,” she forecast.

Vox, an ultra-nationalist party led by Santiago Abascal, has risen from nowhere to become a serious electoral force. Last December it won 12 seats in regional elections in Andalusia, overturning a post-1977 article of political faith in Spain that an avowedly far-right party couldn’t establish itself because of memories of Spain’s long-running dictatorship. Franco ruled Spain from 1939 to his death in 1975.

Ivan Llamazares says Vox, which is attracting Conservative voters angry with Catalan efforts to separate from Spain, “has fragmented the right and pulled its two main parties, the conservative PP and center-right Ciudadanos, to more extreme ideological positions.”

Vox leaders say pollsters are getting it wrong. They maintain they will be able to form a right wing coalition after Sunday’s vote with the PP and Ciudadanos. “I don’t expect the socialists to be able to form a government,” says party official Ivan Espinosa de los Monteros.

Last week Sanchez told supporters at an election rally in his hometown outside Seville that he hadn’t been able in his short stint as prime minister to take on the more ambitious structural reforms he believes the country needs, from overhauling a moribund education system to shaking up labor market regulations. “But we have managed to change its course,” he said.

Sunday’s election will determine whether that is true or not. Or if Spain is heading for greater, paralyzing deadlock.