MADRID — A strong showing Sunday by a pair of upstart parties in Spain's general election upended the country's traditional two-party system, with the ruling Popular Party winning the most votes but falling far short of a parliamentary majority and at risk of being booted from power.
Days or weeks of negotiations will be needed to determine who will govern Spain, with the new far-left Podemos and business-friendly Ciudadanos parties producing shockwaves because of strong support from voters weary of high unemployment, a seemingly endless string of official corruption cases and disgust over the country's political status quo.
If forced out of government, Prime Minister Mariano Rajoy and his Popular Party would become the third European victims this year of a voter backlash against austerity — following elections in Greece and Portugal seen as ballot box rebellions against unpopular tax hikes and spending cuts invoked during the eurozone's debt crisis.
In past Spanish elections, the Popular Party and the main opposition Socialists were the established powerhouses and only needed support from tiny parties to get a majority in parliament when they didn't win one from voters.
But Podemos came in a strong third place and Ciudadanos took fourth in their first election fielding national candidates — setting up a period of uncertainty as parties negotiate with each other to see which ones may be able to form a governing alliance.
"Spain is not going to be the same anymore and we are very happy," said a jubilant Pablo Iglesias, the pony-tailed leader of Podemos.
With 99.9 percent of the vote counted, the Popular Party won 123 seats in the 350-member lower house of Parliament — far below the 186-seat majority it won four years ago after beating the Socialists in a landslide.
The Socialist Party received 90 seats, while Podemos and allies won 69 and Ciudadanos got 40.
Analysts said the outcome will make it extremely difficult for the Popular Party to form a coalition or get voted into parliament as a minority government because it does not get enough seats by allying only with Ciudadanos, its closest possible ideological partner.
The Popular Party would also need support from parties that won 17 seats in the northeastern Catalonia region and are seeking independence from Spain or want more regional financial power and feel alienated by Rajoy's firm rejection of their causes.
And Spain has never had a so called "grand coalition" that would bring the Popular Party and the Socialists together.
Prime Minister Mariano Rajoy told cheering supporters shortly after midnight Monday that he would try to form a government but didn't provide any details of how he might accomplish that goal.
"This party is still the No. 1 force in Spain," Rajoy declared.
But Socialist leader Pedro Sanchez said the result clearly shows "Spain wants a move to the left," adding that he and his party are ready for talks that could lead to a governing accord.
The Socialists could try to team up with Podemos and Ciudadanos in a three-way "coalition of losers" similar to an electoral outcome that happened in neighboring Portugal last month. Also possible for the Socialists is a deal with Podemos plus smaller regional parties that won just a few seats each — not requiring the support of Ciudadanos.
"It looks like a Socialist government," said Federico Santi, a London-based analyst with the Eurasia Group political risk consultancy.
"Reaching a deal between the Socialists, Ciudadanos and Podemos is not going to be straightforward. ... But if the alternative is leaving the country without a government, the pressure will be on the parties."
Podemos and Ciudadanos both gained strength by portraying the Popular Party and the Socialists as out-of-touch behemoths run by politicians who care more about maintaining their own power than citizens' needs.
Miguel Redondo, a 19-year-old Madrid university student, said he voted for Podemos because "it's the party that best understands the difficulties that young people are going through" in a nation where joblessness for people under 25 is more than double the country's overall 21 percent unemployment rate.
Spain's 36.5 million registered voters elected representatives to the lower house of parliament and to the Senate, which has less legislative power. Voting was brisk with lines outside some polling stations and voter participation of 73.2 percent, up from 68.9 percent in the 2011 election.
Francisco Herrera, a 43-year-old porter in Madrid, said he was disappointed with Rajoy's leadership, but voted for the Popular Party because it "defends the economy and the type of government that suits us right now."
The nation's devastating economic crisis, non-stop corruption scandals and a separatist drive in the northeastern region of Catalonia have dominated Spanish politics over the past four years. Rajoy has boasted about his handling of the economy, done his best to skirt the corruption minefield and has vowed to halt the independence push.
His administration's biggest success has been in pulling Spain back from an economic abyss in 2012 and returning the economy to steady growth, but the jobless rate has come down slowly and salaries for people entering the workforce are 30 percent lower than they were in 2008. This fueled claims by Ciudadanos and Podemos that the Socialists plunged Spain into an economic crisis and the Popular Party failed to fix the problem.
Rajoy's party adopted unpopular austerity measures and labor and financial reforms that are credited with creating jobs but blamed for damaging the country's social welfare system. Although Spain's economy is now one of the fastest-growing in the 28-nation European Union, its unemployment rate is the second-highest in the EU after Greece.
Rajoy's administration has also been hurt by his U-turn on a promise not to raise taxes and by cuts to national health care and public education. And many Spaniards are angry about what they perceive as the impunity of politicians and business leaders amid incessant corruption cases.
The question of independence for economically and politically powerful Catalonia has divided that region and soured political ties with the rest of Spain. Rajoy vowed to quash what is seen as the biggest threat to Spanish unity in recent decades. Other parties favor negotiations to devolve more power to Catalonia, and Podemos wants to let Catalan separatists hold a secession referendum.
Rajoy, 60, championed conservative social policies, siding with the Roman Catholic Church against abortion. But he raised questions about his future as the Popular Party leader by including his deputy, 44-year-old Soraya Saenz de Santamaria, on campaign posters.
Sanchez, a 43-year-old former university economics professor, was unknown to most Spaniards until he was elected leader last year of the Socialists.
Iglesias, 37, and his party want to break the mold of Spanish politics. Podemos, or We Can in English, was born from massive Madrid street protests in 2011 that drew mainly young Spaniards weary of corruption.
Ciudadanos, which means Citizens, has the media-savvy Albert Rivera as its leader. At 36, he was the youngest candidate, and his party featured moderate, business-friendly policies plus a pledge to crack down on corruption.
After voting in a Barcelona suburb, Rivera said the election marks the start of a new era — especially for young Spaniards like himself, born after the nation's 1939-1975 dictatorship.
"Those of us who didn't experience the first democratic transition are experiencing a second one," Rivera said.
Associated Press writer Cristina Fuentes-Cantillana contributed to this report.