The ballot will result in a hung parliament, with parties favouring unity with Spain tipped to gain a maximum of 62 seats and pro-secession factions 63.
Wearing yellow ribbons on their lapels to signify support, they filled the length of the Avenue Marina that runs from the beach to Barcelona’s iconic Sagrada Familia church, while the jailed leaders’ families made speeches.
The Supreme Court had summoned them to answer charges of rebellion after they enabled an October 27 declaration of independence that prompted the Spanish government to dissolve the Catalan parliament and sack the regional administration.
Catalonia’s secessionist push has plunged Spain into its worst political crisis in four decades, triggered a business exodus, forced Madrid to cut its economic forecast and reopened old wounds from Spain’s civil war in the 1930s.
Puigdemont, who went to Belgium after his government was fired following a unilateral declaration of independence, said on Friday he was considering standing in the election from Brussels.
The Catalan parliament meets on Thursday to agree on a response to Madrid, and many analysts believe the economically powerful region could formally declare independence.
Police preventing people from voting and firing rubber bullets at protesters, and injuring up to 900, has done deep damage to Spain’s international credibility.