MADRID — Spain’s Socialist Party strengthened its hold on the government on Sunday in the country’s third national election since 2015, with nearly complete results showing growing political polarization and party fragmentation.
The elections came after an abrupt change of government in June, when Pedro Sánchez and his Socialist Party used a corruption scandal to oust Prime Minister Mariano Rajoy’s conservative Popular Party in a parliamentary vote.
Late Sunday, Mr. Sánchez, the current prime minister, declared victory again, even though his party fell short of an absolute majority in Parliament and he will need to find coalition partners to form a government. The Socialists won 123 of the 350 seats in Parliament, with 99.9 percent of the votes counted.
An anti-immigration and ultranationalist party, Vox, won its first seats in Parliament, a major shift in a country that long appeared to be immune to the spread of far-right movements across Europe, in part because of the legacy of the Francisco Franco dictatorship. But its 10 percent share of the vote left it in no position to play kingmaker and help form a governing coalition.
Mr. Sánchez told supporters that his Socialist Party had “sent a message to the world that it’s possible to win against regression and authoritarianism.”
The election results confirmed Mr. Sánchez as one of the great turnaround stories of Spanish politics.
Only two and a half years ago, he was ousted from his own party leadership in an internal revolt. He eventually won re-election, and in June, he became the first Spanish politician to take office by winning a parliamentary vote of no confidence against the incumbent government.
The latest election took place amid a long-running conflict in Catalonia, which was a major issue in the vitriolic campaign. Right-wing politicians accused Mr. Sánchez of treason for trying to negotiate with separatist politicians in Catalonia; the talks got nowhere. The Socialists, on the other hand, warned that the emergence of Vox could help return Spain to the nationalism of the Franco dictatorship.
On Sunday, voters turned out en masse, with 76 percent of the electorate taking part. That was about nine percentage points higher than in the previous election, in 2016.
Amid the high turnout, the main opposition, the Popular Party, had the worst performance in its history, winning only half the seats it got in 2016.
“I don’t think it’s possible to exaggerate the scale of this debacle,” said Cristina Ares, a professor of politics at the University of Santiago de Compostela.
The defeat could help force the ouster of Pablo Casado, who replaced Mr. Rajoy as party leader shortly after Mr. Sánchez won office.
On Sunday, Mr. Casado laid the blame for his party’s “very bad” results on the fragmentation of the right-wing vote. But Santiago Abascal, the leader of Vox, said any blame should rest with the established parties of the right.
Vox promised not only to quash the secessionist challenge in Catalonia but also to recentralize Spain by removing the powers of its regional governments. That platform, however, may have backfired, helping smaller national and regional parties advance on Sunday from the northern region of Cantabria to the Basque Country.
“Vox has been trying to redefine the political game, but we’ve also seen tonight that the reality of Spain is that it is very diverse and regional,” said Juan Rodríguez Teruel, a professor of politics at the University of Valencia.
José Luis Ábalos, a minister in the Socialist government of Mr. Sánchez, said Vox had demonstrated on Sunday that it had “more bark than bite.” He said that Spain “remembers the dictatorship but doesn’t want to go back to it.”
In Catalonia, Esquerra Republicana, a pro-independence party, became for the first time the region’s biggest representative in the Spanish Parliament, rising to 15 seats from nine in the last national election. Esquerra’s leader, Oriol Junqueras, is among a group of politicians who have been held in prison while they stand trial, charged with rebellion and other crimes during a botched attempt to secede in 2017.
The preliminary results suggested that Mr. Sánchez could continue to govern with the support of the same parties that helped him oust Mr. Rajoy from office in June.
Pablo Iglesias, the leader of the far-left Unidas Podemos, said he had called Mr. Sánchez to congratulate him on his victory and offer to form a government with him. Even though Podemos lost voters on Sunday, Mr. Iglesias said his party had helped “put a brake on the far right.”
While Mr. Sánchez is expected to welcome the support of Unidas Podemos, he may decide to steer clear of an uncomfortable alliance with Catalan separatist parties that also helped sink his budget plan in February, forcing him to call a snap election.
Depending on the final breakdown of parliamentary seats, the big unknown is whether Mr. Sánchez could instead try to revive negotiations with Ciudadanos, which on Sunday became the third-largest party in Parliament, almost doubling its share of seats.
Spain’s two-party system was broken up in 2015, when Ciudadanos and the far-left Podemos entered Parliament.
At the time, Ciudadanos was a centrist party and came close to forming a coalition government with Mr. Sánchez and his Socialists. Since June, however, the leader of Ciudadanos, Albert Rivera, has been among the most outspoken critics of Mr. Sánchez and has tilted his party further toward the right, notably after December’s regional election in Andalusia.
Even if the coalition negotiations could be lengthy, analysts said Mr. Sánchez had scored a clear-cut victory that should allow him to avoid a repeat of 2016, when Spain spent almost a year in political limbo following two inconclusive elections, as politicians squabbled over who should govern.
Mr. Sánchez did not win a majority, but “he has now carte blanche to look either to his right or left to form a coalition,” said Jordi Sevilla, a former Socialist minister.
“Even if it’s not going to be easy for him,” he said, “we’ve got to go far back in time to find a party winning an election with double the number of seats of its nearest rival.”
News credit : Nytimes