The most recent Spanish electoral campaign kicks off this weekend; this time it's municipal elections, for city council and mayor, and elections in I believe 13 of the autonomous regions, all except Galicia, the Basque Country, Catalonia, and Andalusia. Election day is May 27.
Remember, in Spain it's not like the US. In the US, on election day, you vote in a variety of different elections on the same ballot. In 2008 you will vote for president, congressional representative, senator (in about 2/3 of the states), governor (in most states), state representative, state senator, atate attorney general, mayor, city council rep, sheriff, and dogcatcher, not to mention different initiatives in the various states. We vote on all these positions, and most people vote for the individual candidate, not necessarily the party. "Splitting your ticket" is very common; that is, you vote for some Democratic candidates and some Republicans, depending on which person (not party) you prefer.
In Spain we only have four kinds of elections: municipal (City Council), regional (the Generalitat in Catalonia), national (the Congress of Deputies and Senate), and European (for the Europarliament). You vote for the party, not the candidate, and seats on the council or in the regional, national, and European parliaments are divided up proportionately. Then the party (or coalition of parties) that wins the most seats puts in its candidate as mayor, regional premier, or Prime Minister.
(Clarification: Of course, many people in Spain choose which party to vote for based on who its leading candidate(s) are. What I mean is your vote doesn't go to, say, Jordi Hereu for mayor of Barcelona; instead, it goes to the Socialist Party, and if they win the election, then their majority on the City Council puts Hereu in as mayor.)
Looks like the big municipal race is going to be Madrid; I don't see Barcelona changing hands, or any of the other major cities. Currently, the PP governs Madrid, Valencia, Málaga, Valladolid, and Palma, while the PSOE governs Barcelona, Sevilla, Zaragoza, and La Coruña. The PP will give the PSOE a run in Sevilla, but that's about it for any hopes of change. The PP dominates most smaller provincial capitals, even in Andalusia.
In the regional elections, the PSOE is going to make a run at PP-held Madrid, Balearics, and Valencia (I don't think they have much chance in any of them), and the PP is going to try to take Aragon and Asturias. The other regions ought to stay in the same hands they're in: Castilla-La Mancha and Extremadura with the PSOE, and Cantabria, La Rioja, Navarra, Castile-Leon, and Murcia with the PP.
For lots and lots of information, check out this groovy special report from pro-Socialist El País (in Spanish).