Pedro Sánchez is the clear winner of Sunday’s snap elections in Spain. With the highest turnout since 1996, the prime minister’s Socialist Workers’ party (PSOE) won nearly double the number of seats of its closest competitor, the conservative Popular Party (PP). But in the country’s highly fragmented political system, it is unlikely to govern alone. Instead, Sánchez must look for support from other parties. Like many progressive parties in Europe, he will have to choose between a technocratic party looking to centralise power and a radical-left party that favours decentralisation.

Sánchez’s victory is the result of two main trends. First and foremost is the rise of Vox, a new, openly misogynistic and xenophobic party that toys with nostalgia for Franco’s dictatorship. Backed by the likes of Steve Bannon, Marine Le Pen and Matteo Salvini, and indirectly financed (via the Madrid-based CitizenGo organisation) by a US super PAC with ties to Donald Trump, Russian oligarch Aleksei Komov and the Italian MP Luca Volontè, who is accused of bribery, Vox rode a wave of anti-Catalan sentiment into the government of Andalucía in December. Sunday’s massive turnout (75.8%) was most likely driven by widespread fear of a rightwing coalition government that would include it.

The second trend that explains Sánchez’s staggering victory is the decline of Unidas Podemos, the radical-left party that emerged in the wake of the anti-austerity indignados movement. Though the party initially promised to implement a progressively participatory new style of politics, over time its leadership has adopted a more traditional top-down approach that has been overly reliant on individual personalities. It lacked proper channels for democratic deliberation, so internal dissent most often took the form of high-profile desertions, such as that of former party leader Íñigo Errejón. It was also recently revealed that a group of police officers have been accused of conducting a smear campaign against the party, with help from government officials. Much was made, too, about the purchase of a pricey chalet by party leaders Pablo Iglesias and Irene Montero, which was depicted in the media as a betrayal of the couple’s leftist ideals.

Together, these factors created a climate of disenchantment around the party that drove almost half of its voters to the socialists or other parties, if not abstention. This is particularly damaging in a country where, historically, a crucial part of the electorate votes for either sweeping change or nothing at all. After 40 years of military rule, Spain’s representative democracy was not designed to reward parties that rely on such a critical mass of voters. But this doesn’t make them any less decisive.

In Podemos’s early days, as its leaders publicly debated what the party’s structure should be, Pablo Iglesias famously responded to one unconventional proposal by saying that then-president Mariano Rajoy could not be defeated by three party leaders, but by one. The party’s spectacular results in the 2015 elections seemed to confirm this view. But Sunday’s outcome suggests that the party might benefit from a more radical approach that gives greater prominence to its social bases and shares the burden of leadership.

If Podemos hopes to win back the voters it has just lost, it will have to distinguish itself from the traditional parties. A radical approach to participation would do much to legitimise its links with social movements and revive its roots in the indignados uprising. After all, the indignados forged a broad consensus by framing the financial crisis and EU-imposed austerity as anti-democratic and demanding a radical democratisation of the economy and the whole of society.

When the new seems impossible, people are tempted to go back to the old ways or to embrace the nihilism of the far right

Towards this end, Podemos could take some cues from the leftwing councils currently governing most of Spain’s major cities, including Madrid and Barcelona. Though not without significant shortcomings, these councils have made citizen participation a crucial part of their brand by organising citizen consultations and participatory budgets. On the other hand, a more radical approach to participation would involve opening the party up to more meaningful forms of deliberation and participation. Over recent years, Podemos’s failure to do so has come off as a disavowal of its initial promise. This is most disheartening because it leaves the impression that a new approach to politics simply isn’t possible. And when the new seems impossible, people are tempted to go back to the old ways or, worse, to embrace the destructive, authoritarian political nihilism of the far right.

In one month, Spain will once again head to the polls to vote for its local governments and the European parliament. In the meantime, Pedro Sánchez’s socialist party will likely enjoy something of a honeymoon period. Outside the party’s headquarters on Sunday, an ecstatic crowd chanted slogans such as No pasarán (“They shall not pass”) and Sí se puede (“Yes we can”), both of which were previously associated with Podemos, the indignados and the anti-fascist resistance before them. Rather than confronting the socialists with inflammatory discourse, Podemos would be wise to remind progressives in Spain, Europe and beyond that another world is possible by putting it into practice.

• Carlos Delclós is a sociologist and associate researcher at the Barcelona Centre for International Affairs (CIDOB). His views do not necessarily reflect those of CIDOB