Ahora Madrid citizen platform's candidate for mayor of Madrid Manuela Carmena takes part in an electoral campaign meeting in Madrid on May 20, 2015
Madrid (AFP) - Manuela Carmena, a 71-year-old retired judge, will become the next mayor of Madrid after her leftist Ahora Madrid protest party on Thursday agreed an alliance with the Socialist party.
"The talks with Socialists to achieve the swearing-in of Manuela Carmena have borne fruit," Ahora Madrid said in a Twitter message.
Carmena -- who will be sworn in on Saturday -- has said that one of her first steps as mayor will be to try to prevent people from becoming homeless by doing away with evictions when possible and providing alternative accommodations when it is not.
She has also promised to stamp out corruption, develop public transport, increase subsidies for poor families and slash the mayor's salary by more than half to 45,000 euros ($50,000).
Ahora Madrid -- born out of the "Indignados (Outraged)" protest movement that erupted during Spain's economic crisis -- came second in local elections on May 24, followed by the Socialists in third place.
Together they hold enough council seats to drive Spain's governing Popular Party out of the city hall stronghold it has controlled for 24 years.
Carmena, who in her youth opposed the Francisco Franco regime, was a largely unknown figure in the Spanish capital before she campaigned on a promise to make the fight against economic inequality her priority.
Her Ahora Madrid platform, a coalition of left-wing groups that was backed by the anti-austerity party Podemos which has shaken up Spanish politics, won 31.8 percent of the vote, giving it 20 seats in city hall.
It came just behind Spain's ruling Popular Party, which fielded Esperanza Aguirre, a former minister and countess by marriage, winning 21 seats.
New centre-right party Ciudadanos won seven seats, not enough to help the Popular Party hold on to power, while the Socialists won nine seats.
Ahora Madrid is without doubt "a unique case in Europe", said Fernando Mendez, a researcher at the Centre for Research on Direct Democracy at the University of Geneva.
Its candidate list as well as its programme were drawn up by "citizens' assemblies" which began in Madrid in June 2014 and were validated by an online vote by over 15,000 people.
The future city councillors who will run the capital city of three million people -- which has an unemployment rate of 16 percent -- will come from neighbourhood associations, collectives and far-left parties like Podemos, the United Left and Equo.
- Podemos ran campaign -
The "Outraged" protest movement against economic inequality and corruption, which occupied public squares across Spain three years ago, also spawned the creation of Podemos in January 2014.
The anti-austerity party, which is close to Greece's ruling Syriza party, came third in 12 of the 13 Spanish regions that voted last month, alongside more than 8,000 towns and cities.
In Barcelona, a female candidate from another citizens' platform of "Outraged" protesters is also expected to take the reins of city hall on Saturday.
Podemos strongly backed Carmena's race to be mayor. The party's leader, pony-tailed professor Pablo Iglesias, regularly heaped praise on her while the party's number two, Inigo Errejon, ran her campaign.
The future spokeswoman for city hall will be Rita Maestre, 26, who also comes from the party.
Carmena, who is known for getting around by bicycle, has promised to govern "not only for those who voted for change" but "also for those who do not believe in it".
Aguirre, her main rival, had tried to convince the Socialists to back her instead of Carmena.
She had warned that allowing Carmena to come to power in Madrid would allow Podemos to "use the mayor's office as a trampoline to break the western democratic system".