Pedro Sánchez may have been the victor in the recent general election but the 123 seats his PSOE party won in Congreso isn't an overall majority. The acting Prime Minister needs to pact, getting enough MPs of other parties to vote for his investiture as new PM, or at the very least get them to abstain.
This week, Sánchez held exploratory talks with the next three parties with most MPs. First in on Monday was Pablo Casado of the conservative Partido Popular. He committed to oppose the investiture, "as official opposition". But in a press conference afterwards, he urged centrist Ciudadanos (Cs) to abstain so that Sánchez didn't have to look for support from the small Catalan separatist parties.
The next morning it was the turn of Cs leader Albert Rivera, who later said he wouldn't be abstaining, preferring to look for a stronger alternative to Sánchez.
Last in was Pablo Iglesias, of left-wing Unidas Podemos, who offered a coalition government with PSOE.
Although a new Congreso is sworn in on 21 May, no deal will be done on the next PM until after the municipal and Euro elections on 26 May.