A total of 92 parties have presented lists in 52 constituencies within the 17 regions, formally known as 'autonomous communities', including the Balearic and Canary Islands. Spain's two remaining North African enclaves, Ceuta and Melilla will also vote.
Just four parties are fighting in all constituencies. They are the Socialist Party, the conservative Popular Party, the United Left and the centrist Democratic and Social Centre.
The voting system, created by the 1978 constitution with the aim of promoting multi- party politics after almost four decades of Franco's one-party rule, is one of proportional representation. Leaving aside the Senate, here is how voting for the Lower House works:
Take Madrid, where there are 34 congressional seats. Each party presents a list of 34 candidates, numbered from 1 to 34. At polling stations, each party list is available on an individual slip. The voter picks a party, rather than candidates, puts the matching slip in an envelope and into the ballot box.
When the votes of Madrid's 3.8 million voters are counted, the 34 seats are allocated on a percentage basis. If, say, the Socialists win 50 per cent of the votes, they get 17 seats. Those seats then go to numbers 1 to 17 on its list. When Felipe Gonzalez enlisted Baltasar Garzon, a leading judge, as an independent on the Socialist list, he gave him the number two spot in Madrid, virtually ensuring him a seat. In the unlikely event that the Socialists won only two seats, they would go to Mr Gonzalez (who is number 1) and Mr Garzon.
The other important areas on 6 June will be the southern region of Andalucia, the two central regions of Castilla-La Mancha and Castilla y Leon, and Catalonia, which have 148 seats between them.Reuse content