MediaLab/ISCTE Detects Portugal's First Documented Indications of External Election Interference — Anonymous Facebook Ads Reached Two Million in Three Days, Cost €12,000

Researchers at the MediaLab/ISCTE, working with the Lusa news agency on the Iberifier disinformation-monitoring project, have documented for the first time what they describe as indícios de interferência externa in a Portuguese election — anonymous, paid online advertising on Facebook targeting the leaders of the two largest parties during the run-up to the 10 March 2026 legislativas. The team, led by Gustavo Cardoso and José Moreno, has been monitoring election communication on Portuguese social and digital media since 2019. Until now, no comparable indication of direct external interference had been recorded.

The investigation focused on two cases. The first ad, anonymous and paid, ran on Facebook, accusing the PS of corruption. The second, also anonymous and also paid on Facebook, tied the PSD leader to the spending cuts of the troika years. According to MediaLab's analysis, the second ad reached more than two million people in just a few days — a scale orders of magnitude larger than what Portuguese parties typically achieve in their official online communication.

The economics of the ad buy are the headline. José Moreno told Lusa that the prohibited online advertising against the PSD leader cost roughly €12,000 over three days — "more than all the parliamentary parties' accounts combined spend in a year" on their official Facebook pages. Drawing on Meta's ad-platform data, MediaLab calculated that the eight parliamentary parties collectively spent €44,975 over five years on their official online ads, an annual average of €8,995. A single anonymous three-day campaign therefore outspent the entire parliamentary-party machine for an annual cycle.

The legal frame matters: the ads ran without identification of the financing source, in breach of the Portuguese Lei do Financiamento dos Partidos Políticos and of Meta's own paid-political-advertising rules. Whoever paid for the campaign — and MediaLab researchers were unable to identify them through the available metadata — operated outside Portuguese transparency law and the platform's policy.

Cardoso's wider reading of the campaign is sharp. He calls the 10 March legislativas the most polarised elections in the history of Portuguese democracy, an assessment that explicitly excludes the presidential cycle, which tends to be polarised by design. He attributes the polarisation to a campaign in which "everyone embarked on the same discourse" of left-versus-right binary, an environment that mechanically widens the channel for disinformation and external manipulation.

The findings will land in front of two institutions. The Comissão Nacional de Eleições (CNE) and the Entidade das Contas e Financiamentos Políticos (ECFP) handle the legal-financing side; the Direção Nacional do Programa de Combate à Desinformação at the Ministry of Internal Affairs handles the security-services side. Iberifier — the EU-funded project hosting the MediaLab work — is part of the European Digital Media Observatory (EDMO) network and the documentation is now in the public record.

For foreign residents, the practical implication is twofold. First, the information environment around Portuguese elections is no longer assumed to be domestic-only — anonymous foreign-origin ads now have to be considered part of the landscape. Second, expat voters registered for the círculo da Europa or the círculo de Fora da Europa rely heavily on online sources, and that channel is exactly where MediaLab found the prohibited advertising. The recommendation that emerges from the report is to prefer whitelisted Portuguese-language outlets and the official party Facebook pages over algorithmically-promoted political content.

Sources: Lusa/Iberifier project page (MediaLab/ISCTE Legislativas 2024 report on the amplification of political discourse and disinformation); MediaLab/ISCTE report by Gustavo Cardoso and José Moreno; Meta ad-library data for the eight parliamentary parties' annual spend.