Catalonia elects a new parliament on Sunday, with the performance of the separatist parties most closely watched after Prime Minister Pedro Sánchez controversially pardoned pro-Catalan independence politicians in order to secure support for his return as head of government.
Former regional head of government Carles Puigdemont, who fled abroad after a failed attempt to declare independence in 2017, is hoping to return to the seat of government in Barcelona.
However, there is still a Spanish arrest warrant out for the 61-year-old, which could only be lifted once the amnesty for the organizers of the 2017 secession attempt that was agreed with the government in Madrid comes into force in June at the earliest.
The election is also seen as a kind of referendum on the controversial amnesty and the question of Catalonia's independence.
According to polls, Sánchez's Spanish Socialist Workers' Party (PSOE) is likely to become the strongest force again with just under 30% of the vote, but will once again fall well short of an absolute majority. It completely rejects independence for Catalonia.
Puigdemont's liberal-conservative Together for Catalonia (Junts) party could finish in second place, just ahead of the party of current regional government leader Pere Aragonès from the separatist Republican Left of Catalonia (ERC) party.
It is completely unclear which government majority could result due to the lack of statements made by the parties on coalition possibilities.
Polls are open between 0700 and 1800 GMT.