His government majority hangs on a few hinge parties, the most progressive ones being Bildu, Podemos and Sumar (arguably in that order) [edit: adding BNGa at the request of a cool comrade below who corrected me]. They haven't even removed the Ley Mordaza (mouthgag law) from the right wing that was applied over a decade ago as a response to the 15-M protests movement.

Additionally, Spain (and hence the PSOE) has a larger maneuvering capability right now due to the economic conditions. Spain, being a deinsdustrialized and tourism-driven economy, is suffering much less from the EU lagging behind industrially compared to China and the USA, than are other countries like Germany or France. Employment numbers are at a historical high for reasons I can't really understand (other than possibly the widespread availability of highly educated Spaniards accepting low-ish wages of 1800€/month drawing the influx of consulting and other service firms, and the growth of tourism, with around twice the Spanish population in visitors each year). This puts the government at an advantageous position, because it can claim on media that "we're the only good™ country where line go up"

However, the growth of the right wing is inevitable, it's a miracle that there's not a right-wing coalition in the government. If only because people get tired of having the same party in power as things get progressively worse (rent prices hiking, stagnating wages, chronical unemployment especially of younger people...), the right wing will almost inevitably win the next elections in a coalition of PP + VOX. The only thing that prevented that from happening last elections was the right wing sabotaging its own capabilities of coalition with regionalist parties of Catalunya/Galicia/Euskal Herria, due to calling them all essentially state-breaking terrorists.