Guardiola's side could complete a first ever domestic treble in English football.
Ivan Rakitic's strike in the first half was enough to see off Real and send Barca 12 points clear of their historic rivals, as well as giving them a 10-point cushion over nearest challengers Atletico Madrid.
Vox, which vehemently opposes illegal immigration and supports the scrapping of tough laws against gender violence, also plans to send a few MEPs into the European Parliament in May elections.
The Socialists, who have ruled the southern region uninterrupted for 36 years, lost 14 seats from the last election in 2015 and are set to lose their grip on power if parties on the right join forces to form a government.
Spanish Prime Minister Pedro Sanchez has said he favours dialogue on Catalonia's future but has ruled out any moves towards independence.
The protests were called online by a grassroots group, Committees for the Defence of the Republic (CDRs), founded to help stage last year's banned referendum and now demanding a clean break with the Spanish state.
Spain's conservative prime minister Mariano Rajoy imposed direct rule on Catalonia after last year's unauthorised plebiscite and called early elections.
A poll by the Centro d'Estudis d'Opinio in July shows 46.7% of Catalans surveyed saying they want an independent state, just ahead of 44.9% who do not.
14 people died - including 2 young children aged 3 and 7 - and over 100 were injured in the Barcelona van attack on the city's most famous street, Las Ramblas, in August 2017.
The Spanish court also dropped European arrest warrants for five other Catalan pro-independence leaders living abroad.
The march had been called by a platform set up in March to "defend Catalan institutions" and "the rights and fundamental freedoms" of its citizens.
"It is very painful because nobody expected it with the lead we had," Iniesta says.
Barcelona leads La Liga by nine points with eight matches left and entertain Real in the penultimate round of the season.
Protesters were walking from Brandenburg Gate to the justice ministry, carrying banners that read "Free Puigdemont and the Catalan political prisoners" and "Spain is not a democracy".
German police had earlier arrested Puigdemont as he crossed the border with Denmark by car, responding to a European warrant issued by Spain.
Puigdemont says if he would have done anything differently, he would not have waited until the 27th to make the independence call.
Luis de Guindos says that Catalonia, which used to be one of the drivers of the Spanish economy, is now a burden.
The election result exposes the flaws in Mariano Rajoy’s strategy and the divisions in Catalan society.