An alliance between Frente Amplio and Podemos could improve their representation in the elections on November 29 without necessarily changing which bloc adds more deputies. The key lies in the origin of the votes and in the provinces where they are concentrated.
The poll by 40dB, published on October 9 by Cadena SER and El País, illustrates this difference: it assigns seven seats to both forces separately and fifteen together. In that second scenario, the PSOE drops from 112 to 106 deputies and PP and Vox go from 198 to 196.
The Congress is distributed province by province
The electoral legislation establishes that deputies are assigned by provincial constituencies, with the particularities of Ceuta and Melilla. There is no national pool where all surplus votes accumulate to obtain representation.
In the provincial distribution, the D'Hondt system is applied: the votes of each candidacy are successively divided and the seats are awarded to the highest quotients. The general legal barrier to participate is 3% of the valid votes cast in the constituency, although exceeding it does not guarantee a deputy.
The electoral sum is not just a mathematical operation
A simulation can keep the votes of two parties intact and calculate what would happen if they ran together. A survey on a joint candidacy poses another situation: voters can change their decision in light of that offer.
Therefore, the seats obtained through a mechanical sum should not be confused with those projected from new voting preferences.
The simulator published this Sunday by El País explores different alliances through hundreds of scenarios. Its utility lies in showing the sensitivity of the distribution, not in turning each combination into a forecast.
What still separates the candidacies
Podemos has proposed open primaries to choose a joint candidacy, with October 14 and 15 as the proposed dates. Frente Amplio initially groups Movimiento Sumar, Izquierda Unida, Más Madrid, and the Comuns.
The negotiation affects both leadership and the composition of the lists. The eventual participation of other territorial forces requires specific agreements.