Center-right People's Party made gains while anti-austerity party Podemos was left disappointed.
The anti-austerity firebrand will forgo a deputy PM role if it blocks a progressive government.
The country's ongoing political deadlock is taking its toll.
The country just wants a new government as soon as possible
After a strong result in a new poll, the party's hand is strengthened ahead of coalition negotiations.
Both parties voiced support for the movement, whilst organisers estimate at least 100 supporters attended.
Pablo Iglesias is on a mission to save Spain.
Pablo Iglesias made the challenge at his 'alternative state of the nation' address on Wednesday.
It will be the party's first major event in the Spanish capital.
Spain’s far-left party have declared their intent to follow in Syriza’s footsteps after election triumph.
Several members of the ETA have spoken of their support for the grassroots political party
Despite the radical left-wing party taking the lead in the Spanish polls, over 50% don't see them as a realistic alternative to the two main parties
Six politicians, including members of the Zapatero administration, allegedly used government funds to acquire works by the Spanish artist at inflated prices and whilst taking a fee
The 10-month-old left-wing party leads the polls, in the biggest ruction of the two-party system since the fall of Franco
As Europe's anti-elite rebellion gains pace, an energetic new Spanish party is surging into the limelight - and becoming a genuine contender for next year's election