The configuration of the Senate has become one of the least visible but potentially most relevant negotiations of the general elections on the upcoming 29th of November. The PSOE is considering running for the Upper House through joint candidacies with the forces positioned to its left and different territorial parties, a formula with which it aims to prevent the PP from repeating the absolute majority it has maintained during the recently concluded legislature. The operation, reported by various media and analyzed this weekend by ElPlural, exploits a very specific characteristic of the electoral system: in a large part of the provinces, coming in first can translate into three senators compared to one from the second candidacy.
According to the simulations published by ElPlural, a joint candidacy of PSOE and Frente Amplio could achieve around 112 directly elected senators in the studied scenario. By adding the four that the calculation attributes to EH Bildu, three to ERC, and one to Agrupación Socialista Gomera, the progressive bloc and its allies would reach approximately 120 of the 208 seats that are directly decided at the polls. These are electoral calculations, not a definitive projection: they depend on polls, on how alliances materialize province by province, and on whether voters from the different formations effectively transfer their support to the common candidacy.
Why three crosses can change the Senate
The explanation lies in the fact that the Senate is not elected in the same way as the Congress. In the peninsular provinces, four senators correspond, but each voter can vote for a maximum of three candidates. Although the lists are open, in practice a large part of the citizens marks the three candidates from the same party, which often results in a distribution of three senators for the most voted candidacy and one for the second. It is not an automatic rule and there are different systems in the islands, Ceuta, and Melilla, but the mechanism generates a strong reward for those who occupy the first provincial position. The Royal Decree of call confirms that on the 29th of November, four senators will be elected for each peninsular province, with the corresponding island and autonomous city exceptions.
This system explains part of what happened in 2023. The PP then achieved 120 of the 208 directly elected senators, while PSOE and Sumar ran separately. A retrospective simulation collected by ElPlural, based on the actual results of those elections, claims that a single candidacy of PSOE and Sumar could have obtained 117 senators compared to 75 from the PP, by becoming the leading force in numerous constituencies where the division of the progressive vote favored the popular party. The exercise serves to show the potential effect of the formula, but it does not demonstrate that the same behavior will be repeated on November 29.
From a proposal by the Ateneo to negotiations between parties
The idea was publicly promoted on October 6 by the platform Senators for Democracy, presented at the Ateneo in Madrid and supported, according to ElPlural, by about 6,500 endorsements. Among its promoters and participants are economists, jurists, unionists, and cultural figures, and its approach consists of progressive formations maintaining different candidacies for Congress but coordinating their names for the Senate.
The proposal has already moved from civil society circles to political conversations. The PSOE acknowledges that it is studying joint candidacies to try to avoid another absolute popular majority, while negotiations intersect with the reorganization of the space to its left around the Frente Amplio. ElPlural points out that socialists and representatives of that space plan to address the issue in their contacts this Sunday. Other media have confirmed that the conversations are more advanced in some territories, including Comunidad Valenciana, Baleares, or Aragón.
The PP has an advantage among the regional senators
There is also a second part of the Chamber that is not decided on November 29. Of the 266 senators that the recently dissolved legislature had, 208 came from the general elections and the rest had been appointed by the regional parliaments. Europa Press estimates that, before the elections, the PP already starts with 23 regional senators, compared to 19 from the PSOE and five from Vox, in addition to representatives from Junts, ERC, BNG, PNV, EH Bildu, Compromís, Más Madrid, Geroa Bai, and Coalición Canaria.
If the new Chamber were to maintain a size of 266 members, the absolute majority would be at 134 seats. That is why a figure like the 120 elected senators proposed by the scenario of ElPlural, added to the representatives designated by the autonomous parliaments, could allow PSOE and its allies to contest or exceed that threshold. But it cannot be stated in advance that the unitary candidacy will "take away" the majority from the PP: the final distribution will depend on the result in each constituency, on the agreements that are actually reached, and on the autonomous composition of the Chamber.
The Constitutional Court, one of the major pending issues
The importance of controlling the Senate is not limited to approving laws or presiding over the Chamber. One of the upcoming major issues will be the renewal of the four magistrates of the Constitutional Court that correspond to be proposed to the Senate. The Constitution establishes that these four members need the support of a majority of three-fifths of the Chamber.
Here appears a fundamental precision regarding the impact of a possible joint candidacy. Having an absolute majority would not allow the left to choose the magistrates of the Constitutional Court on its own. If the Senate were to have 266 members again, the three-fifths would be approximately 160 votes, well above the 134 needed for an absolute majority. Therefore, politically controlling the Chamber would change the negotiating position, but agreements with other forces would still be necessary to make the appointments. The very analysis of ElPlural expressly acknowledges this limit.
And the next CGPJ will also go through the Senate
A similar logic applies to the General Council of the Judiciary. Current legislation establishes that each Chamber elects ten of the twenty members of the governing body of judges: six from the judicial turn and four jurists of recognized competence. All also need a majority of three-fifths.
The current CGPJ began its mandate in 2024 and its ordinary renewal corresponds in 2029, so, unless a new electoral advance occurs, the Senate that comes out of the polls next November could have a decisive role in the election of ten members. Again, an absolute majority of PSOE and its partners would not be enough to make those appointments alone, although it would radically modify the correlation of forces in parliamentary negotiation.
The Cortes are already dissolved and the calendar is tight
The Congress and the Senate were officially dissolved on October 6, after Pedro Sánchez called for early elections for Sunday November 29, 2026. The new Chambers will be constituted on December 23.
The question now is whether the strategy will materialize. The proposed formula would allow PSOE, Frente Amplio, and other forces to maintain their autonomy in the elections to Congress while concentrating part of their vote for the Senate. According to the simulation by ElPlural, this coordination could completely transform the distribution of the Upper House and even end the absolute majority of the PP. But the difference between a simulation and the actual result will be considerable: alliances, candidacies, and, above all, how voters will vote province by province on the next 29-N remain to be finalized.