Swing Spain: Half of All Voters Live in Neighborhoods That Have Changed Sides Since 2008

We tracked 26,395 census sections through Spain's seven general elections since 2008. In the sections that are home to half of the electorate, the conservative People's Party (PP) and the Socialists (PSOE) have traded the lead at least twice. This swing Spain is middle class, with more education than income, and it weighs most exactly where the last seat will be decided on November 29: Tenerife, Huesca, the Balearic Islands, Ciudad Real, Cantabria, Valladolid and Asturias.

21 October 2026 · Miguel · Leer en español

Americans talk about swing states, the states that vote Republican one year and Democratic the next. In Spain, seats are allocated by province, but votes are cast in something much smaller: the census section, a neighborhood or village of 500 to 2,500 voters. There are about 36,000 of them.

We tracked the ones whose boundaries and size have not changed across the seven general elections since 2008: 26,395 sections, home to two in three voters living in Spain. In each one, election by election, we looked at which of Spain’s two traditional big parties was ahead: the conservative People’s Party (PP) or the Socialists (PSOE).

Half of all voters live in swing sections

• Swing (51%). The PP and the PSOE have traded the lead at least twice.
• Flipped once (23%). They changed sides once and have stayed there.
• PSOE strongholds (16%) and PP strongholds (11%). The same party has been ahead every time since 2008.

Swing sections do not change on their own: they ride national waves. In 2008 the PP was ahead of the PSOE in 43% of sections; in 2011, in 75%; in April 2019, in 23%; in 2023, in 49%. Strongholds are the places those waves fail to move.

The back-and-forth between the two big parties is not the same as a switch between left and right. Comparing the left-wing total with the right-wing total instead, only 30% of voters live in sections that switched blocs twice or more. Much of the PP–PSOE flipping comes from votes moving within each bloc: toward Podemos in 2015, toward Ciudadanos and Vox in 2019, and back in 2023.

Who lives in swing Spain

Average across sections, weighted by voters. Net income for 2023; education and unemployment from the 2021 Census.

PP strongholds are mostly well-off neighborhoods, with more college graduates and more older residents. PSOE strongholds are neighborhoods with lower incomes, less education and more unemployment. Swing sections sit in the middle on everything: they are middle class.

To separate the effect of each trait, we compared sections within the same province using a model that takes all of them into account at once.

All else equal, each additional standard deviation in the share of college-educated residents raises the odds that a section swings by 71%; by contrast, each additional standard deviation of income lowers them by 36%, and of people over 65 by 33%. In other words, the sections that change hands are those of educated, middle-aged people without much wealth. The wealthy and the very old tend to be strongholds. This is an association, not a cause: income and education go hand in hand.

Where November 29 will be decided

In our simulations, the PP and the hard-right Vox together win an absolute majority (176 of 350 seats) 99% of the time, but a three-fifths majority (210), the threshold for constitutional amendments, only 23% of the time. What remains open is decided in the last seats of each province, and part of it lies where swing Spain is the majority.

In Santa Cruz de Tenerife, Huesca, the Balearic Islands and Ciudad Real, more than seven in 10 voters live in swing sections, and in Tenerife, Valladolid, Cantabria, Ciudad Real and Asturias the gap between the PP and the PSOE in those sections was under two points in 2023. In Barcelona, Tarragona, Navarre, Biscay and Gipuzkoa the last seat is also a toss-up, but there the PP–PSOE contest is not what decides it.

Six cities, section by section

Hover over (or tap) any section to see its code, the PP–PSOE margin in 2023 and how many times it has changed hands.

What this analysis does not say

• A third of voters are left out. Sections that have split or grown a lot since 2008, mostly new neighborhoods, have no comparable series.
• A swing section is not a prediction. It means the section has changed hands before with national waves, not that it will on November 29.
• The PP–PSOE comparison does not work everywhere. In Catalonia, the Basque Country and Navarre, nationalist and regional parties shape the contest; in Navarre, the PP also ran jointly with the regional UPN until 2019.
• Association, not cause. The profile describes where swing sections are, not why they swing.

How we calculated it

• Results. Interior Ministry polling-station results for the 2008, 2011, 2015, 2016, April and November 2019 and 2023 general elections, added up by census section, excluding votes from Spaniards abroad, as a percentage of valid votes.
• Stable sections. The same code in all seven elections and a registered electorate that changed by no more than 10% relative to its municipality between each pair of elections.
• Categories. By how many times the order between the PP and the PSOE flipped across the six transitions. Blocs: left (PSOE, IU-Podemos-Sumar, Más País, Compromís, ERC, Bildu, BNG, CUP, Geroa Bai) vs. right (PP, Vox, Ciudadanos, UPyD, CiU-Junts, PNV, CC, UPN, Foro); some nationalist parties are hard to place.
• Profile. INE (Spain’s statistics office) Household Income Distribution Atlas (2023) and 2021 Census. Logistic model with province fixed effects.
• Maps. INE census sections as of January 1, 2023.
• Code. analisis_secciones.py, focalizacion.py, geo_secciones.py and articulo_bisagra.py, in the altnalysis repository.