Thousands of young Spaniards angered over unemployment have taken to the streets across the country, demanding a boycott of the big political parties in local elections on Sunday.
The movement, coordinated through online social media, marks a shift in Spain where up to now people have scarcely protested against the European Union's highest jobless rate, a stagnant economy and government spending cuts.
Most of the protesters are young, from what the International Monetary Fund has called Spain's potential "lost generation", given youth unemployment of 45 per cent.
"We want politicians who are concerned about our lives, not their own political and economic interests," said a spokesman for one of the protest movements, tomalaplaza.net, surrounded by campers who spent the night under awnings in Madrid's Puerta del Sol square. The man, in his 20s, declined to give his name.
Thousands of protesters who filled Puerta del Sol on Sunday and Monday were removed by police yesterday, then more returned last night. Protesters called the plaza 'Solution Square' and covered it banners demanding 'Real Democracy Now' and slogans such as 'Don't vote for them'.
Some 200 camped out overnight and were cleaning up and arranging their tarpaulins on Wednesday morning. Authorities in Madrid and Granada rejected requests for rallies to be held later in the day.
"We're not afraid. We've been saying for days that we're not going away," one of the protesters said on Cadena Ser, Spain's most popular radio station.
The protesters, who also gathered in dozens of other cities around the country, are calling on people not to vote for the ruling Socialists or centre-right opposition Partido Popular in 8,116 municipal and 13 regional elections on Sunday.
Politicians from both parties have been implicated in corruption scandals in their traditional strongholds.
Government spending cuts aimed at avoiding a fiscal crisis that could trigger a fourth euro zone bailout have worsened the hangover from a housing boom and bust. Spanish growth is lagging that of central Europe and is not robust enough to create jobs.
Prime minister Jose Luis Rodriguez Zapatero's popularity has crumbled, but labour union protests against layoffs have been muted, partly because of strong ties with the ruling Socialists.
Thousands also demonstrated in Barcelona, Palma de Mallorca, Valencia, Granada, Santiago de Compostela, Vigo and Bilbao.
But voters outside of Catalonia and the Basque Country, which have strong regional parties, have few alternatives to the two-party system which has controlled national politics since Spain became a democracy in 1978.
Smaller nationwide parties such as the United Left (IU), itself tainted by corruption accusations, have seen their representation squeezed by Spain's voting system, which favours large national parties and strong regional ones.
Abstention or voting for small parties is seen as damaging for the Socialists, who are expected to lose some city and regional governments they have controlled for decades.
The Partido Popular, in opposition for eight years at the national level, is expected to make major gains on Sunday, possibly foreshadowing a return to power in general elections due by March next year.
The protests have captured the mood of young Spaniards, many of whom have their lives on hold as they search for work, and sites related to the movement occupy three of the top trending topics on Twitter for Spain.
"This is about being an outsider in your own country. There is the sense that the youth is the most important thing in a country, they should be providing the cutting edge ideas, they should feel like they are the future," said David Bach, a specialist in strategy and economics at Madrid's IE business school.