Spain: Opinion poll by Sigma Dos on 12/05/2025

The Spanish Parliament (Cortes Generales) is bicameral, consisting of the Congress of Deputies (Congreso de los Diputados) and the Senate (Senado). The Congress has 350 members elected via proportional representation with closed lists. The country is divided into 52 constituencies (the provinces plus the autonomous cities of Ceuta and Melilla). Seats are allocated using the D'Hondt method. Because many provinces elect only a small number of deputies, the system effectively behaves like a majoritarian one in rural areas, favoring large national parties and strong regionalist movements.

To enter the Spanish Congress of Deputies, a party must secure a minimum of 3% of the valid votes. Crucially, this threshold is applied at the constituency level, not nationally. In practice, this 3% rule is often irrelevant in smaller provinces, where the limited number of seats means the effective threshold to win a mandate is much higher (frequently exceeding 10% or 15%). The 3% clause only becomes a significant factor for smaller parties in large constituencies like Madrid or Barcelona.

Government formation in Spain centers on the Congress of Deputies. After consulting party leaders, the King nominates a candidate for Prime Minister (Presidente del Gobierno). In the first round of voting, the candidate needs an absolute majority (176 votes). If not achieved, a second vote is held 48 hours later, requiring only a simple majority (more "yes" than "no" votes). While Spain was traditionally dominated by a two-party system, it has shifted since 2015 toward multi-party dynamics requiring complex coalitions or minority governments supported by various parliamentary groups.

This overview shows all parties that, based on current polling, have a realistic chance of entering parliament in Spain or significantly shape the political debate. Classifying their political orientation is essential for understanding bloc formation and the mathematically possible majorities in the next parliament.