Shouting "yes we can" and "unity", thousands of Podemos supporters gathered Saturday at a decisive two-day meeting in Madrid that could unseat the charismatic leader of one of Europe's leading far-left parties.
Born in 2014 out of the Indignados anti-austerity protest movement that swept Spain during a severe economic crisis, the party, an ally of Greece's Syriza, has found itself riven by in-fighting after a meteoric rise to national-level politics.
But on Saturday, party leaders attempted to put these bitter divisions behind them as they took to the stage in a congress centre bathed in purple flags and banners, the colour of Podemos, in an electric atmosphere.
"We have committed many mistakes," Pablo Iglesias, the party's charismatic leader and co-founder, said on stage behind huge white letters spelling out Podemos.
To wild applause, the 38-year-old added the weekend's congress should be "an example of fraternity, unity and intelligence".
For months, Iglesias and his deputy and former close friend Inigo Errejon, 33, have been locked in a high-profile duel over how to steer the party towards taking power now that it has become Spain's third most powerful political force.
Supporters are hoping the deep and damaging rift will be put to rest by Sunday, when they elect a new leadership council and secretary general, with Iglesias presenting his candidacy again.
Crucially, they will also vote on a strategy for moving the party forward.
After a meteoric rise that saw it shatter Spain's traditional two-party system, coming third in 2015 general elections and in a repeat 2016 vote, Podemos now finds itself at a crossroads.
Should the party, which harnessed the anger of millions stung by Spain's economic crisis, take to the streets again as an anti-establishment group, as wanted by Iglesias and his followers?
Or should it shed an "enfant terrible" image that may be scaring away voters now that it has become a credible political force, and work from within parliament as Errejon and his supporters propose?
The congress caps three intense years for a party that went from nothing to securing millions of votes in general elections, on a promise of radical change and a more egalitarian society.
But for some supporters, the months of in-fighting have left their "scar", as 49-year-old Rafa Burguillo put it.
He travelled to Madrid for the congress from Barcelona with his wife Eva Campos, a Podemos councillor, and their eight-year-old son.
"When people get a taste of power, they really like it. And they forget that what they actually have to do is debate to change the system," he said.
Burguillo is a supporter of Iglesias, and will be voting for him and his list of candidates for the leadership council.
"He remains true to his ideas, to a hard, strong discourse."
Two self-imposed challenges loom for Podemos: replacing the Socialists as Spain's main opposition party, and eventually taking power.
Iglesias' and Errejon's differences over how to do this have created friction as party members have picked sides, prompting accusations of a purge against dissenters by those close to the Podemos chief.
On Saturday, though, the pair put on a united front, appearing on stage together along with other leaders from either side.
Both teams have drafted competing lists of candidates for the leadership council.
Errejon is not standing for secretary general, which means Iglesias will almost certainly be re-elected as Podemos chief, since the only other candidate is a low-profile lawmaker.
But Iglesias has said that if his list of candidates for the leadership council and his strategy are not approved, he will step aside.
That would set the scene for a second crisis within Podemos as the party tries to replace him.
But supporters at the congress hope it won't come to this, Errejon included.
"From Monday, more Podemos, more together, stronger," he told the crowd, to huge applause.