The socialist candidate's mistaken vote in Granada: a statistical gift for the PSOE
Olga Manzano, the PSOE candidate in Granada, went to the wrong electoral table and cast her ballot in the wrong box. The Electoral Board decided to annul a vote at random from the affected ballot box, a remedy that, according to probabilistic analysis, statistically favours the PSOE.
The incident and its far-fetched solution
Last Sunday, during the Andalusian elections, the socialist candidate confused her table and voted at one that was not hers. The polling station, instead of stopping her, allowed her to insert her ballot. Once the mistake was discovered, the Electoral Board ruled that Manzano's vote could not be cast again and chose to annul a vote at random from the box where she had voted improperly. A solution several analysts have called "far-fetched".
The statistical bias of annulling a vote at random
The key point of the debate is the bias introduced by random annulment. According to previous poll data, the probability that the annulled vote belongs to a party other than the PSOE is 75%. Since the candidate presumably voted for her own party, the net effect is equivalent to her having inserted two socialist ballots: one real and one fictitious, by annulling someone else's vote. "It's as if she had put in TWO ballots," one analysis sums up. The only way not to harm anyone would have been to leave the ballot box as it was.
Shared incompetence
Although the candidate bears the main responsibility, the polling station also failed by not checking whether the voter was on the list. The Electoral Board's decision to annul a vote at random instead of challenging the entire ballot box has been harshly criticised. Some argue that the right thing would have been to repeat the vote at that table on another day. Random annulment, besides being biased, has no clear precedent and could be challenged in court.
The open question is whether the applied solution has not turned out worse than the original mistake, and whether the socialist candidate has not, unintentionally, achieved the same as if she had voted twice.
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