Elections in Spain: why they call it a useful vote if it can harm them

Since many decades, the big parties have advised to issue a "useful vote" for the elections to the Congress of Deputies. Thus, some voters understood that their vote was worth much more if they opted for a party with options to get seats, but that they voted for another party for which polls predict that they would vote. they would not win any seat. In such a case, these voters usually have a strategic vote, that is, they do not vote for their favorite party, but for another less desired party, but with a seat option.

The most useful vote for every voter is perhaps the sincere vote, that is, the party that best represents their ideals. If no party is acceptable, the "useful vote" is the blank vote.

Are the 287,000 votes obtained by PACMA in 2016 not useful because PACMA has not obtained any seats? It is true that an almost identical number of votes gave 5 seats to a nationalist party, which gave the party considerable power. But the results of PACMA, perhaps somewhat reduced by the effect of the "useful vote", have conveyed to politicians and society in general the message that many people oppose the wrong animal treatment.

The vote of a voter in the congressional elections does not usually change, that is to say that the result of the distribution of seats hardly ever changes to change his vote from one party to the other. # 39; other. But when many voters, for example 1% or 2%, issue the same strategic vote, they can benefit from the party that receives them at certain seats.

For example, it is well known that in the past, some UI supporters voted for the PSOE in medium or small districts because they did not have the opportunity to obtain a seat and that this strategy could change a seat of the PP. to the PSOE in an opportunity. The same could happen with the transfer of PP votes from mid-sized or small center-right parties, with whom a PSOE seat could switch to PP.

Now, what will happen if the same "useful vote" strategy is applied when trying to attract the vote of a party that is ideologically close, with less good prospects but with the possibility of winning a vote? seat? In this case, the benefit obtained in elections prior to 2015 does not guarantee that it will occur at the present time. Even worse, this strategy can hurt the party calling for a "useful vote".

Let's look at a simulation using data from recent surveys. Sunday's public agenda brought together the following voting trends: PSOE 28.1%, PP 20.2%, C 15.4%, 13.5%, VOX 12.7%. Suppose these percentages appear next Sunday in one of the many districts in which they occupy three seats, then the distribution would be 1-1-1-0-0.

The first thing we observe is that the most favored party would be the C, getting the same seats as the PSOE and the PP, despite a much lower percentage of votes. This did not happen before 2015, because then the recipient was the winner who had won two seats and the second party a seat.

Now, let's look at another scenario in the same constituency, in which we badume that the call for "useful vote" of the PP moves 2 points of sympathizers from C to the PP, leaving the PP at 22.2% and the C to 13.4%. With which the seat of C pbades to Podemos and the effect would have been, indirectly, the opposite of that desired by the PP with its call for "useful vote".

Again, badume that the same voting patterns materialize in a 5-seat constituency. The players would be 2-1-1-1-0, Podemos being the most favored, while PP and VOX would be the most affected. but if the PSOE had called for "useful vote" and if a number of voters of Podemos equivalent to 2 points, it would have changed its vote in PSOE, with which POSE would have 30.1% and Podemos 11.5%, the result of the new distribution is as follows: We could lose the seat in favor of VOX without the PSOE having benefited from this vote transfer.

Again the call for "useful vote" would have the opposite effect to the one desired. Both examples show that the effect of the "useful vote" is uncontrollable in the elections to the Congress of Deputies. The result is a lottery. Receiving votes from a nearby party by emphasizing the "useful vote" can be beneficial or harmful.

This scenario in which five state-level parties have the opportunity to sit in many districts and in which constituency parties do not have to be the two most voted, as was the case in the past. can not guarantee that large parties receive a higher premium than smaller parties.

This has already occurred in the last elections to the Andalusian Parliament, where the PSOE, which was voted most, is not the one with the lowest vote cost per seat, and VOX, which was the least voted (among those who obtained representation), had the highest cost of votes per seat.

Our electoral systems produce this uncertainty because they have not been modified by a more just system, in which each party receives a percentage of seats very similar to its percentage of votes and the winning party is the most popular.

Thus, on Sunday, we will again have discords and imbalances in the representation of parties in the Congress of Deputies and, perhaps, resurgent new demands for electoral reform. In the meantime, it is preferable that each party tries to attract the voters' vote by offering better solutions to the major problems of society, rather than demanding the so-called "useful vote", as this may be detrimental to them .

Victoriano Ramírez González: Professor of Applied Mathematics at the University of Granada, University of Granada