Jais Adam-Troian

Eric Bonetto
email: eric.bonetto@univ-amu.fr

Florent Varet
email: florent.varet@univ-lille.fr

Thomas Arciszewski
email: thomas.arciszewski@univ-amu.fr

Théo Guiller
email: theo.guiller@univ-amu.fr

Pathogen Threat Increases Electoral Success for Conservative Parties: Results from a Natural Experiment with COVID-19 in France

Keywords: Coronavirus, pathogen threat, COVID-19, election, conservative, behavioral immune system Coronavirus, pathogen threat, COVID-19, election, conservative, behavioural immune system

Conservative ideology is closely linked with pathogen prevalence, and adherence to conservative values increases under pathogen threat. To this day, few studies have demonstrated this effect using ecological voter data. For the first time, we analyse results from an election (the 2020 French local election) which was held during the growing COVID-19 spread in the country. Using mixed modelling on county-level data (N = 96), we show that perceived COVID-19 threat (search volume indices) but not real threat (prevalence rates) prior to the election are positively associated with an increase in conservative votes only. These results were robust to adjustment on several covariates including abstention rates, prior electoral scores for conservative parties, and economic characteristics. Overall, a 1% increase in COVID-19 search volumes lead to an increase in conservative votes of .25%, 95%CI [.08,.41]. These results highlight the relevance of evolutionary theory for understanding real-life political behaviour and indicate that the current COVID-19 pandemic could have a substantial impact on electoral outcomes.

INTRODUCTION

The world is currently undergoing a pandemic of COVID-19, a novel coronavirus. As of April 10, 2020, 1,521,252 people were diagnosed with a COVID-19 infection and 92,798 died from the virus (WHO, 2020). With a case fatality rate estimated around 2-3% [START_REF] Cao | COVID-19 case-fatality rate and demographic and socioeconomic influencers: worldwide spatial regression analysis based on countrylevel data[END_REF], COVID-19 represents a potent and salient global threat. So far, the health and economic impacts of COVID-19 have been subjected to extensive assessment (McKibbin, & Fernando, 2020).

However, few studies have investigated its political consequences [START_REF] Karwowski | When in danger, turn right: Does covid-19 threat promote social conservatism and right-wing presidential candidates[END_REF].

Incidentally, the current pandemic occurred at the same time as local elections in France, which gave us an unprecedented opportunity to directly assess how prevalence of COVID-19 may impact electoral outcomes in vivo. More specifically, we expected that COVID-19 threatas a pathogen-caused infection (SARS-COV-2)would increase preference for conservative parties [START_REF] Terrizzi | The behavioral immune system and social conservatism: A meta-analysis[END_REF].

Current evolutionary theories of political psychology converge in linking pathogen threat and social conservatism [START_REF] Thornhill | Parasites, democratization, and the liberalization of values across contemporary countries[END_REF]. In fact, pathogens come with high costs for their hosts, which have facilitated the evolution of anti-pathogen defence mechanisms.

Besides a physiological immune system that deals with pathogens inside the organism, humans have developed a parallel immune system to monitor, detect and actively avoid physical contact with pathogens (the so-called 'behavioural immune system'; [START_REF] Schaller | The behavioural immune system and the psychology of human sociality[END_REF]. This system is designed to favour behaviours that reduce interpersonal contacts -hence limit one's likelihood of contracting infectious diseases.

Accordingly, individuals display increased risk aversion, introversion and decreased openness to experience under pathogen threat [START_REF] Schaller | Pathogens, personality, and culture: Disease prevalence predicts worldwide variability in sociosexuality, extraversion, and openness to experience[END_REF]. Similarly, ecological pathogen prevalence is associated with the development of collectivistic cultures which tend to be more socially conservative (e.g., more adherence to norms and traditions ;[START_REF] Varnum | Pathogen prevalence is associated with cultural changes in gender equality[END_REF]. For example, evidence suggests that the 2014 Ebola outbreak did influence electoral preference for conservative candidates during federal elections held later that year [START_REF] Beall | Infections and elections: Did an Ebola outbreak influence the 2014 US federal elections (and if so, how)?[END_REF]see Schaller et al., 2017 for a replication).Likewise, historical prevalence of non-zoonotic diseases predicted conservative votes for the 2016 US presidential election [START_REF] Zmigrod | The Psychological and Socio-Political Consequences of Infectious Diseases: Authoritarianism, Governance, and Nonzoonotic (Human-to-Human) Infection Transmission[END_REF], and research suggests that ideology differently relates to threat sensitivity, with liberals being more sensitive to economic threats while conservatives to pathogen related ones [START_REF] Fiagbenu | Of deadly beans and risky stocks: Political ideology and attitude formation via exploration depend on the nature of the attitude stimuli[END_REF].

From this perspective, it is expected that the threat posed by COVID-19 could trigger temporary shifts in ideological preferences in favour of conservatism, which could affect immediate electoral outcomes. Supporting a social conservative-shift under COVID-19 threat, a longitudinal study among Californian residents revealed that individuals reported higher adherence to gender role conformity and gender stereotypes during the pandemic compared to before [START_REF] Rosenfeld | Can a Pandemic Make People More Socially Conservative? Longitudinal Evidence from COVID-19[END_REF]. Thus, we hypothesized that COVID-19 threat would increase electoral success for conservative parties. This hypothesis was recently tested in a series of experiments manipulating COVID-19 threat salience. Among representative samples of US and Polish citizens, COVID-19 threat was found to increase preference for conservative ideology and conservative political candidates [START_REF] Karwowski | When in danger, turn right: Does covid-19 threat promote social conservatism and right-wing presidential candidates[END_REF].

Despite this robust converging evidence, there remains a lack of studies assessing the impact of current (vs. historical) pathogen prevalence on electoral outcomes directlyfor obvious reasons. Therefore, it is still not clear whether pathogen threat from ongoing non-zoonotic diseases could carry over and 'go to the ballot'. The present study was precisely set up to address this issue in the context of the 2020 local elections in France. There, elections were maintained though COVID-19 was spreading across the country, yielding a unique opportunity to test our hypothesis. To do so, we measured real pathogen threat using COVID-19 cases counts and perceived threat from volumes of online search related to COVID-19 (due to high media coverage).

METHODS

Data collection

Electoral outcomes

France is divided into several layers of governance, from municipalities ('communes'; N = 34,968) inserted in counties ('départements'; N = 101), themselves part of larger territories ('régions'; N = 18). Here, we examined voting shares for different parties during the French local (municipality) elections which took place in March of 2020. These elections are run on two-rounds, according to a proportional representation scheme with a majority premium for larger municipalities. Despite the COVID-19 pandemic, authorities maintained the first round on March the 15 th , but the second (March the 22 nd ) was subsequently cancelled.

Our electoral outcome data represents the share of votes for each party at the end of the first round -for municipalities of more than 1,000 inhabitants. These were obtained through a press application which aggregates data from municipalities at the department level, using raw data from a State repository1 . The same application allowed us to retrieve scores for the previous local election of 2014 to obtain adjustment variables (previous voting shares for different parties). From this data, we computed voting shares by summing the percentage of votes for parties with similar ideologies (see Appendix 1 for details).

COVID-19 Threat

We decided to use two measures of COVID-19 threat. First, we gathered the number of diagnosed COVID-19 cases, available at the county-level 2 ('département') as aggregated by the French health authorities on March 10 (5 days before the elections). We then divided these by population size for each county to obtain a COVID-19 prevalence rate, normalized per 100,000 inhabitants. Besides this 'objective' threat indicator, we also needed a 'subjective' index of individual exposure to actual threat. At this time in France, the COVID-19 pandemic was not as widespread as now and many counties only had a handful cases. This meant that COVID-19 was probably limited to a few local clusters, and not necessarily threatening to most individuals living in the same geographical cluster. Thus, we decided to include search volume indices (i.e., Google Trends) for the words 'COVID-19', 'coronavirus' and 'covid' (α = .73) averaged over the time period preceding the elections (January 1 st -March 14 th , 2020) and into a single score. This index, ranging from 0 to 100 reflects the percentage of search terms related to COVID-19 -normalized relative to the highest search volume -and constitutes a proxy for individual online exposure to pathogen threat-related contents. In fact, search volume data reliably taps into collective perceptions and have been found to predict offline behavior in various domains (e.g. [START_REF] Preis | Quantifying trading behavior in financial markets using Google Trends[END_REF].

Social & Economic Indicators

We collected a series of potential socio-economic confounds from the French National Institute for Statistics and Economic Studies (INSEE3 ). These included the most up-to-date statistics for population census, unemployment, poverty and mortality rates as well as average per capita income.

Analytic Strategy

Our final dataset (accessible at https://osf.io/pvmjf/) included 96 counties (101 minus oversea territories for which COVID-19 and election data was not available). Because these counties belong to several territories ('régions'), spatial clustering needed to be accounted for. Thus, we decided to test our hypotheses using mixed modelling [START_REF] Schielzeth | Nested by design: model fitting and interpretation in a mixed model era[END_REF]. In addition, sensitivity analyses would be carried out by running models both with and without covariates, including potential confounds such as prior electoral outcomes. Overall, the study's biases due to its observational nature would be partly balanced by careful consideration of crucial confounds, and variable design (COVID-19 threat indicators temporally precede March 15 electoral outcomes).

RESULTS

COVID-19 Threat indicators

A first mixed-model was run to assess the relationship between our two COVID-threat .47, 95%CI[.29,.65], p < .001 (r²marginal = .17). Therefore, objective and perceived COVID-19 threat were linked but did display some considerable non-overlap. The same models were re-run using conservative and extreme right-wing votes as outcomes.

Hypothesis Test

Importantly, the effect of COVID-19 was driven by an increase in conservative votes β = .25, 95%CI[.08,.41], p = .004, (Model r²marginal = .09) while extreme right-wing votes were overall unaffected β = -.01, 95%CI[-.02,.01], p = .06 (figure 1). This led us to consider conservative votes as the main study outcome for increased accuracy (results are similar using general rightwing votes). As expected too, no relationship was observed between our threat indicators and other types of political parties -thus not reported.

[INSERT FIGURE 1 HERE]

Sensitivity Analyses

We ran another mixed-model dropping COVID-19 prevalence to assess whether the effect of search volume was spurious, but the effect remained stable on conservative votes β = .21, 95%CI [.06,.35], p = .007. Finally, we computed a model with relevant covariatesincluding 2014 conservative votes -to probe the artefactual nature of our results, specified as:

Conservative votes ~ 1 + (1 | region) + COVID-19 Prevalence + COVID-19 Search Volume + 2014 Conservative votes + Abstention rates + Population + Income + Mortality +

Unemployment + Poverty. Although these improved model fit with comparable parsimony (Restricted Maximum Likelihood, AIC = 592, r²conditional = .54; r²marginal = .57), the effect of COVID-19 search volumes remained unchanged, β = .24, 95%CI[.09,.39], p = .003. The full model table can be found on the OSF project page (https://osf.io/pvmjf/)

DISCUSSION

To the best of our knowledge, this study is the first of its kind to assess the direct impact of a global pathogen threat on electoral outcomes, thus ecological voter behaviour. Current psychological theories of threat regulation predict that COVID-19a deadly, anxiogenic, societal threat -would lead to either polarization (i.e. increased extremist votes; [START_REF] Jonas | Threat and defense: From anxiety to approach[END_REF][START_REF] Pyszczynski | The Role of Death in Life: Exploring the Interface Between Terror Management Theory and Evolutionary Psychology[END_REF], increased right and far-right votes [START_REF] Jost | Ideological asymmetries and the essence of political psychology[END_REF] or even in left votes (because these parties are perceived as more competent to manage health-related issues; see [START_REF] Eadeh | Can threat increase support for liberalism? New insights into the relationship between threat and political attitudes[END_REF]). Yet, as predicted by the Parasite Model of Democratization and Behavioural Immune System Theory, we did observe a positive association with perceived COVID-19 threat prior to the election and electoral success of conservative parties only. These findings highlight the power of evolutionary theorizing to explain human reactions to ecological threats.

The effect of COVID-19 threat was robust to adjustment on several potential confounds including prior electoral success of conservative parties. Replicating recent results from [START_REF] Zmigrod | The Psychological and Socio-Political Consequences of Infectious Diseases: Authoritarianism, Governance, and Nonzoonotic (Human-to-Human) Infection Transmission[END_REF] and [START_REF] Karwowski | When in danger, turn right: Does covid-19 threat promote social conservatism and right-wing presidential candidates[END_REF], we confirmed that pathogen threat effects can translate into real-world political outcomes, extending well-known effects of historical pathogen threats on ideological preferences to ongoing pandemics. With a 1% increase in pathogen threat salience is associated with between .08 to .41% supplementary votes for conservative parties. This moderate effect size is in line with meta-analytical estimates of the links between behavioural immune system mechanisms and social conservatism [START_REF] Terrizzi | The behavioral immune system and social conservatism: A meta-analysis[END_REF].

In addition to these empirical findings, our study identified two boundary conditions of interest for evolutionary political science [START_REF] Petersen | Evolutionary political psychology: On the origin and structure of heuristics and biases in politics[END_REF]. First, the effect of COVID-19 on conservative votes was only observable when measuring perceived (exposure to online materials related to the pandemic) and not necessarily real (prevalence rates) threat. This underlines the crucial role of media and public communication in shaping collective perceptions of the pandemic andpossiblytheir political consequences. Moreover, COVID-19 threat effects only seemed to affect conservative, not extreme-right wing votes. This finding aligns with prior evidence showing that xenophobia and out-group prejudice tend to be more related to parasite stress (albeit weakly; [START_REF] Tybur | Parasite stress and pathogen avoidance relate to distinct dimensions of political ideology across 30 nations[END_REF] and not necessarily pathogen prevalence [START_REF] Thornhill | Parasites, democratization, and the liberalization of values across contemporary countries[END_REF]. Still, these results point at the need to separate conservatism and xenophobia when assessing pathogen threat effects on voting and raise the question whether similar political gains could extend to non-conservative candidates (e.g. liberals) using arguments emphasizing conservative values.

Limitations

The present findings' implications should be conditioned to some caveats that we will now discuss. First and foremost, the study design remains observational. Even if pathogen threat measures were taken prior to the elections and that major confounds have been controlled for, we cannot exclude the influence of non-measured confounding variables. For example, historical county-level prevalence of infectious diseases (especially non-zoonotic ones) might relate to current pathogen threat perceptions (e.g. through cultural transmission) and ultimately explain the observed relationship between COVID-19 search volumes and conservative votes.

For lack of available data, we could not rule out this explanation. Future research designs should therefore include both current and historical pathogen prevalence to assess the presence of confounding or mediation mechanisms (see [START_REF] Fiedler | Unwarranted inferences from statistical mediation tests-An analysis of articles published in 2015[END_REF].

Other limitations pertain to field constraints and cultural specificities that warrant caution when generalizing the effects. In the face of growing COVID-19 cases, the French authorities decided to suspend the elections, which bounded our data to results from the 1 st round of a 2-round election. Although this does not invalidate the findings themselves, replicating these results when voters' choice is restricted to only a few alternatives might constitute a stronger test of Behavioural Immune System Theory [START_REF] Platt | Strong inference[END_REF]. For instance, in absence of conservative candidate(s), would voters still prefer the 'relatively' more conservative candidate(s) available?

Relatedly, French politics have specific features that should be taken into account. Compared to the US for instance, French conservative parties tend to be more socially liberal: they support women's access to free abortion and would not argue against universal healthcare. To the extent that French conservatives are still more socially conservative French liberals (on issues such as same-sex marriage), our test remains valid, but cross-cultural moderators should be considered when generalizing the findings to other contexts (see [START_REF] Malka | Are cultural and economic conservatism positively correlated? A large-scale cross-national test[END_REF].

Finally, we demonstrated that pathogen threat perceptions were driving increases in right-wing votes. This finding is important because actual COVID-19 threat's effects could paradoxically decrease during the pandemic (e.g., perceptions of low number of cases) or increase after the pandemic is gone (e.g., reminders of the pandemic in public discourse and the media).

Therefore, the political effects of pathogen threat may be further modulated by structural factors such as freedom of press (i.e. prevalence of pro-government information) or healthcare systems' efficacy in managing the pandemic.

Conclusion

Within the inferential boundaries of this study, we are confident that our results constitute original robust evidence for the existence of a pathogen threat effect on electoral outcomes. We hope these findings stimulate further research on the ecological determinants of electoral success, and inform policy makers regarding decisions to maintain or delay elections during global threats such as pandemics. We conclude that the current COVID-19 pandemic could substantially contribute to electoral successes for conservatives, in areas where threat perceptions remain salient.

  indicators, specified as follows: COVID-19 Search Volume ~ 1 + (1 | region) + COVID-19 Prevalence. The model was adequate (Restricted Maximum Likelihood, AIC = 674, r²conditional = .44). It highlighted a positive link between COVID-19 prevalence and search volumes β =

A

  mixed-model was run to assess the relationship between COVID-19 threat and general rightwing votes, specified as follows: Right-wing votes ~ 1 + (1 | region) + COVID-19 Prevalence + COVID-19 Search Volume. The model was adequate (Restricted Maximum Likelihood, AIC = 636, r²conditional = .32; r²marginal = .08). It indicated no noticeable effect of COVID-19 prevalence, β = -.08, 95%CI[-.25,.08], p = .33, but a substantial positive effect of COVID-19 search volume β =.23, 95%CI[.07,.40], p = .007. Thus, it seemed that perceivednot realpathogen threat was linked with increased right-wing votes.

FIGURESFigure 1 .

 1 FIGURES

https://www.data.gouv.fr/fr/datasets/elections-municipales-2020-resultats/ available from https://www.challenges.fr/politique/infographie-municipales-retrouvez-la-carte-des-resultatsdu-premier-tour-ville-par-ville_702873

2 https://www.santepubliquefrance.fr/recherche/#search=COVID-19%20Point%20épidémiologique

https://statistiques-locales.insee.fr/#bbox=-997689,6661347,2487500,1619645&c=indicator&view=map2

Appendix 1.

Unlike the bipartisan political system prevalent in the US, French politics is defined by the coexistence of several parties that often overlap in terms of ideology. These typically gather a few percentage of total votes and may cooperate or compete at different levels and institutional times.