In countries across the world, online misinformation – or ‘Fake News’ – is distorting elections with populist leaders and parties exacerbating this challenge, often employing conspiracy theories and other forms of political misinformation to attract voters. For instance, populist narratives attribute blame for adverse events or conditions on powerful and undeserving groups or elites who conspire to hide their influence from the general public (Hawkins 2009; Mudde and Rovira Kaltwasser 2012; Mudde and Rovira Kaltwasser 2013). Despite the growing importance of fake news in politics, we know little about which types of people are most susceptible to fake news and about how to effectively combat it.
To shed light on these questions, we conducted survey experiments in Spain with a sample of 8,000 participants that resembled the Spanish population in terms of gender, age, education, and region of residence. We focused in particular on the role of populist and conspiratorial attitudes, examining whether voters who hold these attitudes are more susceptible to fake news and/or resistant to fact checks.
Respondents began the experiment with a “practice question” in which they indicated their belief in the true claim that human activity is causing more extreme weather events. Respondents then read short news articles about several false claims, all of them related to fake news items that had circulated in Spain shortly before the experiment was conducted. For the purposes of this research, the items were divided into four groups of fake news with different degrees of populism and conspiratorial content (table 1). All respondents read one claim from each of the following four groups, and were then asked to indicate whether they considered that the information was very accurate, somewhat accurate, somewhat inaccurate or very inaccurate.

Figure 1 shows that 85% of respondents considered that the first news item, i.e., the story that linked human action to climate change, was true (as, indeed, is the case). However, belief in the other claims, all of which are false, varied. At the high end, more than half of respondents (52.1%) believe that patent holders are restricting the supply of cancer drugs in order to drive up prices.
At the other extreme, only around one-in-ten respondents (11.3%) believe that the central government is considering ways to reduce language classes and replace them with religious studies. In turn, 18.6% of respondents believed that vaccination increases the risk of autism, a false claim with potentially very serious implications for public health. Although this figure is comparatively low, it is still troubling that nearly one in five respondents holds a misperception that could lead them to eschew potentially life-saving vaccines.

Who is more likely to believe in fake news? And what role do populism and conspiratorial thinking play? Populist rhetoric emphasizes the division between ‘the people’ and ‘the elites’ embedded in a moral (Manichean) discourse, a ‘good-versus-evil’ understanding of the world and politics (Mudde and Rovira Kaltwasser 2013; Hawkins 2010).
Conspiratorial rhetoric, too, emphasizes secret plots by powerful actors, but reaches beyond the political sphere to include broader societal phenomena. In our survey, we measured respondents’ affinity towards populism and their degree of conspiracism using scientifically validated attitudinal scales (Castanho et al. 2019 and Bruder et al. 2013). For the analyses below, we divided our sample into different groups: respondents above and below median populism respectively, and respondents above and below median conspiracism.
Figure 2 reveals similar patterns between populist predispositions, conspiratorial thinking, and belief in false claims. More than 55% of respondents with high levels of both populist and conspiratorial predispositions are susceptible to misinformation involving genetically modified foods, a claim that does not involve any elite actor. In addition, the same type of respondent is more prone to accept news stories that do involve colluding elites: for example, the claims referring to pacts between parties to block the participation of the opposition, or those dealing with clandestine NATO operations or profit-seeking pharmaceutical patent holders. However, it is interesting to note that respondents with high levels populist or conspiratorial attitudes do not differ in their reaction from the rest of the respondents when it comes to the claims about changes in the school curriculum, even though both stories involved a clearly identified elite actor (in this case, central government).

Are factors other than populist or conspiratorial attitudes related to belief in false claims? The results of a series of regression models, shown in table 2, point to a striking correlation: respondents who reported seeking news on social media (Whatsapp, Facebook, Twitter) are more likely to believe all eight false claims included in our study. While these results cannot be taken as causal, they nonetheless suggest that social media use may increase exposure to and belief in false news stories.
Respondents we class as “populist” show a greater propensity to believe five out of the eight fake news items, particularly those involving colluding elites (political or otherwise). Respondents with a conspiratorial mentality, on the other hand, gave more credit to items that suggest broader conspiracies: claims about withheld medicines, clandestine fumigation or the risk posed by genetically modified foods.

Are there partisan differences in belief in fake news? In our study, Vox and Podemos voters stand out, as they appear inclined to believe claims that are consistent with their political preferences. This is consistent with a psychological process known as motivated reasoning, in which people unconsciously seek to validate their pre-existing beliefs when processing information, resulting in a cognitive bias (Flynn et al. 2017).
The results suggest that affective evaluations of the elites involved in the claim (PP for Podemos voters, PSOE for Vox voters), together with the salience of the issue depicted, played a fundamental role for respondents’ belief in the accuracy of the false claim. Similarly, conservative respondents appear inclined to lend credence to false claims when they align with preconceived ideological constructs.