The acting prime minister of Spain, Pedro Sánchez, in Níjar (Almería). Europa Press

For nearly 40 years, the post-election talks that the Spanish king holds with political parties to determine who will try to form a government in Congress were a dull formality. Everyone knew ahead of time what the others would say, who would submit to what is known in Spain as an “investiture vote,” and who would vote for and against the candidate.

What seems least likely of all – although with Iglesias there are no certainties – is that Podemos’s 35 lawmakers will vote in favor of Sánchez

But all that changed in 2016. That year Pablo Iglesias, the leader of the leftist party Unidas Podemos, informed Felipe VI about an offer for a coalition government with the Socialist Party (PSOE) that the latter had not been told about.

Fast-forward to today. Neither one of Spain’s four largest parties – PSOE, the Popular Party (PP), center-right Ciudadanos (Citizens) and Unidas Podemos – really knows what the others will tell the monarch at a fresh round of talks that will be decisive: if no solid candidate emerges in the coming days, parliament will be dissolved next week and a repeat general election called for November 10. It would be the fourth in Spain in as many years.

And while audiences are by now getting used to last-minute plot twists engineered by Pablo Iglesias, this time it was Albert Rivera of Ciudadanos who came up with an unexpected offer. On Monday, Rivera said his party could abstain at the investiture vote, as long as the PP does so as well, and only if the PSOE agrees to certain conditions involving taxes, the government in the northern Spanish region of Navarre and the Catalan separatist crisis.

Ciudadanos came in third at the April 28 election, and its 57 seats would be enough to help the PSOE – which has 123 lawmakers in Congress – to form a government. But Rivera had lately chosen to side with the conservative PP and the far-right Vox, explicitly shunning any deals with the Socialists.

Meanwhile, Unidas Podemos’s Iglesias on Monday announced that he is still planning to abstain even if the PP and Ciudadanos do so as well. This would guarantee that acting Prime Minister Pedro Sánchez can finally form a government, after failing at an earlier investiture vote held in July. Following Spanish electoral legislation, the candidate needs an absolute majority of votes in the first round, or failing that, a simple majority of more yes than no votes in a second round, meaning that abstentions play a key part.

What seems least likely of all – although with Iglesias there are no certainties – is that Unidas Podemos’s 35 lawmakers will vote in favor of Sánchez, making abstentions by other parties irrelevant. Iglesias and Sánchez have been at odds over the possibility of a coalition government, something that the former demands and the latter rejects.

Playing in Sánchez’s favor is the fact that he will be the last political leader to meet with the king, at which point he will already know what all the others have said. In theory, he could save his own investiture by reaching a last-minute deal with either Unidas Podemos or with Ciudadanos and the PP.

But the time for agreements is coming to an end. Any investiture session will have to take place this weekend, before parliament is automatically dissolved on September 23 and a new election called for November 10.