Spain's Senate on November 29 with today's polls, not the 2023 vote: the left's joint ticket is not enough, and a three-fifths majority is in play

On the 2023 vote, a joint Senate ticket of the Socialists (PSOE) and Frente Amplio would hand the left control of the Senate. On today's forecast it would not: the conservative People's Party (PP) wins a majority on its own in 60% of simulations, and with the hard-right Vox in 81%. And the three-fifths majority that PP leader Alberto Núñez Feijóo is seeking, out of reach on the 2023 figures, comes up in half of the scenarios if Vox stands aside in 19 districts or agrees joint 2+1 tickets.

21 October 2026 · Miguel · Leer en español

Spanish daily El Mundo publishes today a useful calculation: what the 2023 Senate would have looked like had the PSOE and Sumar run on a single ticket, as the PSOE and Frente Amplio will now do in most provinces. On those votes, the left would have won 135 senators, an absolute majority, against 109 for the PP and Vox. To win it back, Vox would have had to stand aside in 17 provinces, and even withdrawing everywhere the right would not have reached three fifths of the chamber.

The calculation is right for the 2023 vote. But Spain will not vote on November 29 as it did in 2023. We repeated the exercise with today’s altnalysis forecast, across 50,000 simulations, and the conclusion changes.

What has changed since 2023

The PSOE starts five points below its 2023 result and Vox six points above. In the Senate, where the most-voted list in each province usually takes three of the four seats, a swing of that size flips many provinces, and the left’s joint ticket no longer makes up for what it has lost.

Who wins the majority, depending on the right’s deal

Senators in the full chamber, elected and appointed by regional parliaments: median and, in brackets, the 95% range of the simulations.

• Without any deal, the right already holds a majority in 81% of simulations, and the PP alone in 60%. The PP and Vox falling short of 134 is still possible, in about one scenario in five, but it is no longer the expected outcome.
• The 135 senators El Mundo gives the left on the 2023 vote sit at the edge of our range: the joint ticket has a median of 98 and reaches 135 only in roughly the most favorable 2.5% of scenarios.
• A Vox withdrawal mainly helps the PP: it lifts the PP’s chance of a majority on its own from 60% to 92%. It adds little to the bloc’s absolute majority, which it already had.

Three fifths: from impossible to a coin toss

With three fifths of the Senate, 161 seats, the chamber can appoint four Constitutional Court justices and ten members of the General Council of the Judiciary without the opposition. According to El Mundo, Feijóo said yesterday that this is his goal. On the 2023 vote it was out of reach. On today’s forecast:

• No deal: the PP and Vox reach 161 in 19% of simulations.
• With 2+1 lists (two PP candidates and one from Vox on a joint list in 16 provinces): 48%.
• If Vox does not run in 19 districts: 51%.

In other words, the deal being negotiated between the two parties decides less whether the right will hold a majority, which is already likely, than whether it gets three fifths, which goes from one chance in five to one in two.

The offer of regional senators

Feijóo has hinted that the PP could give Vox some of the senators appointed by regional parliaments in exchange for standing aside in some provinces. Those 58 senators are chosen by the regional parliaments according to their current makeup (today, 23 PP and 5 Vox). Handing some to Vox changes the split within the bloc but adds no seat to the PP and Vox total: what moves the majority and the three fifths is the withdrawal in the provinces, not the swap.

Why we differ from the 2023 calculation

• Votes. El Mundo uses the 2023 results; we use the November 29 forecast, with its uncertainty: the polls and their historical error, the vote by province and the overseas vote.
• Which provinces. El Mundo picks, among the provinces where Vox won less than 13% in 2023, the 17 where its withdrawal would give the PP seats. Our two scenarios use the 19 districts in the scenario published by El Español on October 19: Valencia, Seville, Castellón, Asturias, Badajoz, Cádiz, Pontevedra, Huelva, Cáceres, Alicante, Jaén, Granada, Zaragoza, Guadalajara, Córdoba and Huesca, plus the Balearic Islands, Las Palmas and Santa Cruz de Tenerife.
• Where Vox voters go. El Mundo assumes every Vox vote goes to the PP. We assume between 55% and 85%; the rest abstain, vote blank or back other parties.
• The left’s joint ticket keeps, in our model, between 90% and 100% of what the PSOE and Frente Amplio would have won separately; it does not run in the Catalan provinces, in Seville or in several Canary Islands districts.

What this analysis does not say

• It does not forecast deals. The three scenarios are hypotheses: how the PP and Vox will run will not be known until candidacies are formally proclaimed, around November 3.
• It carries a lot of uncertainty. The Senate is very sensitive to small shifts in each province; the 95% ranges reflect that.
• It does not say how senators will vote. It counts seats by list, not future loyalties.

How we calculated it

The altnalysis Senate forecast of October 21 (50,000 simulations): in each one, the four senators of each province (three on the larger islands and one on the smaller ones; two each in Ceuta and Melilla) are allocated by each list’s expected vote under the Senate’s limited vote, and the 58 regional senators are added. Absolute majority: 134 of 267; three fifths: 161. Details in the methodology and the data in Data.