Electoral system

The Spanish Cortes Generales are envisaged as an imperfect bicameral system. The Congress of Deputies has greater legislative power than the Senate, having the ability to vote confidence in or withdraw it from a prime minister and to override Senate vetoes by an absolute majority of votes. Nonetheless, the Senate possesses a few exclusive (yet limited in number) functions—such as its role in constitutional amendment—which are not subject to the Congress' override.^[4][5] Voting for the Cortes Generales is on the basis of universal suffrage, which comprises all nationals over 18 years of age and in full enjoyment of their political rights.

For the Congress of Deputies, 348 seats are elected using the D'Hondt method and a closed list proportional representation, with an electoral threshold of three percent of valid votes—which includes blank ballots—being applied in each constituency. Seats are allocated to constituencies, corresponding to the provinces of Spain, with each being allocated an initial minimum of two seats and the remaining 248 being distributed in proportion to their populations. Ceuta and Melilla are allocated the two remaining seats, which are elected using plurality voting.^[4][6] The use of the D'Hondt method may result in a higher effective threshold, depending on the district magnitude.^[7]

As a result of the aforementioned allocation, each Congress multi-member constituency would be entitled the following seats (as of 23 December 2023):^{[lower-alpha 3]}

For the Senate, 208 seats are elected using an open list partial block voting system, with electors voting for individual candidates instead of parties. In constituencies electing four seats, electors can vote for up to three candidates; in those with two or three seats, for up to two candidates; and for one candidate in single-member districts. Each of the 47 peninsular provinces is allocated four seats, whereas for insular provinces, such as the Balearic and Canary Islands, districts are the islands themselves, with the larger—Majorca, Gran Canaria and Tenerife—being allocated three seats each, and the smaller—Menorca, Ibiza–Formentera, Fuerteventura, La Gomera, El Hierro, Lanzarote and La Palma—one each. Ceuta and Melilla elect two seats each. Additionally, autonomous communities can appoint at least one senator each and are entitled to one additional senator per each million inhabitants.^[4][6]

Election date

The term of each chamber of the Cortes Generales—the Congress and the Senate—expires four years from the date of their previous election, unless they are dissolved earlier. The election decree shall be issued no later than the twenty-fifth day prior to the date of expiry of parliament and published on the following day in the Official State Gazette (BOE), with election day taking place on the fifty-fourth day from publication. The previous election was held on 23 July 2023, which means that the legislature's term will expire on 23 July 2027. The election decree must be published in the BOE no later than 29 June 2027, with the election taking place on the fifty-fourth day from publication, setting the latest possible election date for the Cortes Generales on Sunday, 22 August 2027.^[6]

The prime minister has the prerogative to dissolve both chambers at any given time—either jointly or separately—and call a snap election, provided that no motion of no confidence is in process, no state of emergency is in force and that dissolution does not occur before one year has elapsed since the previous one. Additionally, both chambers are to be dissolved and a new election called if an investiture process fails to elect a prime minister within a two-month period from the first ballot.^[4] Barred this exception, there is no constitutional requirement for simultaneous elections for the Congress and the Senate. Still, as of 2024 there has been no precedent of separate elections taking place under the 1978 Constitution.