The Senate elections have traditionally been relegated to a secondary role in the general elections, overshadowed by a Congress in which the investiture is decided and on which the continuity of the Government depends. On November 29, however, the Upper House will have an unusual importance due to a majority that until now had barely entered the electoral discussion, that of the three-fifths that would allow the right to face the pending renewal of the Constitutional Court without the left.
The dispute is therefore not limited to who will have the absolute majority in the Senate. The result could open the door to a change in the balance of the Constitutional Court and, at the same time, has led progressive sectors to seek formulas to concentrate a vote that, due to the particularities of the electoral system of the Upper House, can translate into several seats in each province.
In this context, this Tuesday in Madrid Senators and Senators for Democracy is presented, an initiative that emerged from civil society that demands joint candidacies from leftist forces. Its promoters do not only aim to prevent PP and Vox from reaching the three-fifths, but to take advantage of the election system of the senators to try to contest the absolute majority even from the right.
The Constitutional Court, the key to the three-fifths
The Senate has pending since the end of 2025 the renewal of the four magistrates of the Constitutional Court that it is responsible for proposing, for which the Constitution requires a three-fifths majority. The mandates of Cándido Conde-Pumpido, María Luisa Balaguer, Ricardo Enríquez, and José María Macías expired on December 17, although the four continue in their positions until they are replaced.
The renewal could again alter the balance of a court that currently has seven magistrates considered progressive and five conservatives. The majority last changed at the beginning of 2023, after the four members designated at the end of the previous year by the Government and the General Council of the Judiciary joined, two from each institution, ending the predominance that the conservative sector had maintained until then.
Those magistrates were appointed, in general, for nine years, so that this third of the court will not be renewed until 2031. The four positions that now depend on the Senate thus constitute the most immediate possibility of modifying the current majority, without waiting another five years for the next renewal of that block.
For the right, the difference between achieving or not achieving the three-fifths is therefore substantial. If PP, Vox, and the forces that may support them reach that majority and agree on the candidates, they will be able to push through the four appointments without negotiating with the left. Below that threshold, they will have to seek support outside their block.
The change does not allow for anticipating the direction of future rulings, as the magistrates exercise their functions independently, but it can change the balance of an organ that will have to resolve the appeals of unconstitutionality that are presented against the laws approved during the next legislature.
The left seeks to concentrate the vote for the Senate
The possibility that the right reaches the three-fifths has focused the left's attention on a Chamber that has traditionally received much less attention during campaigns. This Tuesday, Senators and Senators for Democracy is officially presented at the Ateneo de Madrid, which calls on PSOE, Sumar, IU, Podemos, Más Madrid, Compromís, and other progressive forces to explore joint candidacies in the different constituencies.
Among the people linked to the promoting group are Cristina Almeida, Javier Pérez Royo, Gloria Elizo, Bruno Estrada, Cristina Monge, and Juan Torres. Their proposal is based on the idea that the division among similar candidacies can particularly penalize in the Senate, while concentrating votes on the same names allows competing for more positions in each province.
The declared objective goes beyond preventing PP and Vox from reaching the necessary majority to renew the Constitutional Court without agreeing with the left. The platform aims to contest the absolute majority of the Senate from the right, for which it intends to extend electoral agreements among the different progressive formations.
The formula has precedents. In previous general elections, different forces have reached agreements to present joint candidacies for the Senate in certain constituencies, although the initiative launched now aims to expand that strategy for the 29N.
How senators are elected and why alliances can be decisive
Unlike what happens in Congress, in Senate elections, closed party lists are not voted on, but individual candidates. The voter can choose names from the same party or distribute their votes among candidates from different parties, a peculiarity that makes electoral coordination a much more important factor.
The general rule establishes that each peninsular province elects four senators, although each citizen can vote for a maximum of three candidates. The four names that receive the most support obtain the seats, without a proportional distribution among parties as is applied to elect members of Congress.
This limited voting system explains that usually the most voted candidacy obtains three senators and the second one gets the fourth, as long as their respective electorates concentrate their votes on the names presented by each party. When several parties from the same space run separately, however, their candidates may end up competing against each other to be among the four most voted.
There lies the interest of joint candidacies. If several forces present the same candidates and manage to get their voters to concentrate their support on them, they increase their chances of placing them among the top positions, although the agreement does not guarantee any result because each voter retains the freedom to combine names from different parties or to use only part of their votes.
The distribution is different in the island territories and in the autonomous cities. Gran Canaria, Mallorca, and Tenerife each elect three senators, while Ibiza-Formentera, Menorca, Fuerteventura, La Gomera, El Hierro, Lanzarote, and La Palma elect one. Ceuta and Melilla each have two.
To the senators directly elected at the polls are added the designated by the autonomous communities, which have one initially and another for each million inhabitants. Their election corresponds to the respective autonomous parliaments, so the final composition of the Upper House does not depend exclusively on the votes cast on November 29.