Madrid gains a seat and Cádiz gives one up: the new map of seats

The Congreso will still have 350 seats at the general election of 29 November 2026, but not all of them will be elected where they were in 2023. Under Real Decreto 806/2026, of 5 October, which dissolves the Cortes and calls the election, Madrid goes from 37 to 38 deputies and Cádiz drops from 9 to 8. The other 50 constituencies keep exactly the figure they had at the last election.

The shift is small, one seat going one way and another coming back, but it has the merit of reminding us that the electoral map is not a fixed piece of furniture. Each election reassembles it from the same parts and a rule written into law, and sometimes a part ends up in a different drawer.

A fixed floor and a share-out that moves

The rule is set out in Article 162 of the Ley Orgánica del Régimen Electoral General. Each province is guaranteed 2 seats, Ceuta and Melilla elect 1 each, and the remaining 248 are distributed according to population. The first part is immovable; the second is the one that is recalculated, and the one that explains why a deputy changes province.

Because the total is fixed at 350, the system works like a game of musical chairs in which no chairs are ever added: if one province gains a seat, another has to give one up. When a province's weight in the proportional share-out shifts enough, the marginal seat changes hands, and this time the decree moves it from Cádiz to Madrid.

Under the new allocation, Madrid strengthens its position as the constituency that elects the most deputies. It is followed by Barcelona with 32, València/Valencia with 16, Alacant/Alicante and Sevilla with 12 each, Málaga with 11 and Murcia with 10, according to the figures in the royal decree. Cádiz, with its 8 seats, joins the group of five provinces that elect that number.

At the other end, the fixed part of the law is far more noticeable. Ceuta and Melilla elect 1 deputy each, Soria elects 2, the provincial minimum, and Zamora, Teruel and Segovia elect 3. In fact, the most crowded section of the map is not at the top but at the bottom: there are 8 provinces with 3 seats, 10 with 4 and another 8 with 5.

What would have changed with the 2023 votes

To see the practical effect of the change, Su Momento has allocated the votes from the 2023 general election, using the final results from the Ministerio del Interior, by the D'Hondt method, with both the seat numbers of that time and those of now. The exercise isolates the effect of the rule: same votes, different number of seats.

In Cádiz, with 8 seats instead of 9, the PP would have gone from 4 deputies to 3 with those votes. In Madrid, with 38 instead of 37, the PSOE would have gone from 10 to 11. In both provinces, the other parties would have kept the same seats they won in 2023.

This simulation should be read for what it is: an illustration of the effect of the change, not a forecast of anything. The 2026 votes will be different, and the last seat in each province, the one D'Hondt settles by margins that are sometimes narrow, may fall one way or the other for reasons that have nothing to do with the allocation. Anyone wishing to try other scenarios can do so in the simulator.

One seat, fifty-four days

There are 54 days to go until 29 November, some 8 weeks in which the map will no longer move: the decree has set how many deputies each constituency elects, and that is the figure that will count at the ballot box. What does remain to be decided is who fills each seat.

Details on the two provinces affected can be found in the profiles for Madrid and Cádiz, and any reader can check how many seats are at stake in their constituency via My province. For the remaining 50, the news is that there is no news, which, in an electoral system, is also a form of stability.