From Peruvian literature to Soviet military history, Catalan independence to Jeremy Corbyn’s Labour party, there are, it seems, very few subjects on which Pablo Iglesias does not have an enthusiastic opinion.

But wide as the scope of his interests and knowledge is, his immediate focus is on the Podemos congress this weekend, an event that will determine the direction of the anti-austerity party he leads and, very possibly, make or break his political career.



Three years after it emerged from the indignados movement to shatter Spain’s traditional two-party system, Podemos is facing a profound political and philosophical dilemma. Others might call it a civil war.



“Podemos needs to understand that politics is about institutions and government, but it’s also about a family that can’t make it to the end of the month, about a school’s parents’ association; it’s about students who can’t pay their tuition fees and pensioners whose pensions don’t go far enough or who have to pay a lot for their medicines,” Iglesias told the Guardian.



Despite their differences Iglesias says ‘Iñigo Errejón brings a lot to Podemos’. Photograph: Javier Soriano/AFP/Getty Images

And that, he argues, is why the party needs to think beyond parliament and remain an engaged popular movement attuned to the fears and desires of Spaniards. His position has put him and his followers – dubbed pablistas – at odds with his old friend Iñigo Errejón, who is number two in Podemos.

This weekend will give the party faithful the chance to choose between – and vote on – Iglesias’s vision and that of Errejón. “There are two projects, two teams, two leadership alternatives and it’s good that our members can choose the option they find more convincing,” said Iglesias.

Errejón and the errejonistas favour a more pragmatic and less fiery approach. They have pushed for closer ties with the Spanish socialist party (PSOE) and questioned the wisdom of Podemos’s decision, just before last June’s inconclusive general election, to run on a joint ticket with United Left (IU), a leftwing coalition that includes the Communist party of Spain.



The June vote proved a turning point: despite polls suggesting that Unidos Podemos was on course to bring about a historic upset by leapfrogging the PSOE to finish second behind the conservative People’s party, it didn’t happen. The party came third. Worse still, the new coalition lost 1.2m of the votes its constituent parties had won separately at the previous general election in 2015.



Iglesias defends the joint strategy, pointing to the success Podemos has enjoyed by entering into coalitions in Catalonia, Galicia and Valencia: “I think it all adds up to change; we’re capable of governing in Spain’s most important town halls because we were capable of allying ourselves with other forces.”



Of the poor election result, Iglesias says he thinks ‘the pressure was too great and it made us soften our message too much’. Photograph: Andrea Comas/Reuters

He offers an alternative explanation for June’s disappointment.



“I think the pressure got too much for us: all the polls said we could come second and some even said we’d be neck-and-neck with the People’s party. I think that pressure was too great and it made us soften our message too much. I think some people in the country felt we were losing the sincerity and credibility we’d had before.”



Iglesias is, however, careful to stress that the party was then barely two-and-a-half years old, and that “going from non-existence to winning 5 million votes and becoming the primary political force in Catalonia and the Basque country, and the second in Madrid, is impressive going”.



However, the election results quickly – and publicly – revealed the party’s tactical and ideological faultlines.



Last September, Errejón tweeted: “We already scare the powerful; that’s not the challenge. It’s about seducing those among our people who are suffering but still don’t trust us.”



Iglesias replied: “Yes … but in June, we stopped seducing a million people. We’ll seduce more by speaking clearly and being different.”



Speaking clearly has not always been a problem for the 38-year-old former political science professor. A famous video clip from parliament shows Errejón’s discomfort as Iglesias reminds the socialists of their role in the dirty war against Basque sepratists group Eta in the 1980s, when government-funded death squads murdered suspected terrorists and disposed of their bodies. Iglesias told the chamber that the former PSOE leader, Felipe González, was a man with “a quicklime-stained past”.



Podemos has changed the traditional two-party system in the Spanish parliament. Photograph: Pablo Blazquez Dominguez/Getty Images

Not for nothing was Podemos once described by a Spanish sociologist as “a half-formed political animal, a coalition of pretty varied interests that’s kept together by electoral success and by the drive to occupy new space”.



The public disagreements – not to mention online skirmishes between the two factions and a battle for control of Madrid, where the party was born – have tossed the party’s opponents ammunition by the magazineful.



Iglesias concedes that those who claim Podemos is undisciplined and unprofessional have a point.



“There are debates that we need to have in our own house and not in the media,” he said. “It’s fine to be transparent but we don’t need to be naive. We’re still a new political force that’s maturing and we need to come out of this new congress stronger and more united.”

If Iglesias wins this weekend, he promises to stretch out his hand and try to bring unity to the party. If he loses, the play is clear: he will step down as leader but will never abandon the party.



“I don’t want to be secretary general if my ideas are minority ones and if my team ends up in the minority. It seems to me to be a question of consistency: we can’t tie ourselves to our chairs; we have to assume that, politically, we’re just passing through.”



The pressures of politics have put paid to the carefree days of academia when he and Errejón would hold “very lively and very intense” intellectual discussions that lasted for hours and ended with a beer.

“Now the situation is different and I think it’s fundamental that we separate the personal and the private from the political,” he said. “[But] I think Iñigo Errejón brings a lot to Podemos.”



But wouldn’t the project be easier without his old friend in the party? “Not at all. It’s the absolute opposite: I want to have the best people close to me even if they don’t think like me.”



Iglesias feels he has grown up a lot over the past three years, learned to cope with the pressure and is far better prepared to be prime minister. All he needs to do now is survive the weekend.



“Being in politics broadens the shoulders,” he said. “There’s that cruel saying: ‘What doesn’t kill you makes you stronger.’ And I think the punches we’ve taken have made us stronger.”