SPAIN goes to the polls on Sunday for local and regional elections, seen as a bellwether for the general election in December.

Recent polls show the conservative Popular Party may be gaining ground on the ruling Socialists in key regions.

Spain’s 17 regional governments, plus two autonomous cities, have budgetary discretion over education, health, housing and policing. 

Twelve of them and the two cities will be contested on Sunday. Other key battles include the selection of mayors for the country’s two largest cities, Madrid and Barcelona.

Polls released last week by Spain’s CIS public research institute showed the Spanish Socialist Workers Party, or PSOE, is just 0.3 percentage points ahead of the Popular Party in the regional vote.

In Madrid, the right-wing Isabel Diaz Ayuso is seeking re-election for a third time as regional president.

But in Spain’s second-largest city, Barcelona, socialists appear to be gaining support where current mayor, Ada Colau, is running neck and neck with the Socialists, her coalition partners.

With contests coming down to very slim margins in regions like Aragon and the Balearic Islands, the 17.6 per cent of voters who declared themselves undecided in the last opinion poll will have an outsize role in deciding the outcome.