Abstract: Understanding the political consequences of digitalization is among the key challenges for modern societies. A pressing issue is the question whether political online activities make individuals more close-minded and less willing to consider alternative arguments. We examine this question using a peculiarity of the Swiss electoral system – the possibility to split votes – as a behavioral outcome measure. We argue that political online activities might either make individuals less likely to split votes (“echo chamber”-argument) or more likely to spread their votes across parties (“deliberation”-argument). Empirically, we use data from the Swiss Election Study Selects 2019 to test these arguments. The results of a hierarchical logistic regression analysis do not support any of the conflicting arguments. Yet, additional analyses suggest that political interest moderates the relationship between online activities and vote splitting: political interest makes online activists more likely to split votes. Eine grosse Herausforderung für moderne Gesellschaften besteht darin, die politischen Folgen der Digitalisierung zu verstehen. Zentral ist hierbei die Frage, ob online ausgeübte politische Aktivitäten dazu führen, dass Menschen weniger offen für andere Meinungen und alternative politische Argumente sind. Wir nutzen eine Besonderheit des Schweizer Wahlsystems, um diese Frage zu untersuchen: die Möglichkeit des Stimmensplittings („Panaschieren“). Somit können wir untersuchen, ob politische Aktivitäten im Netz und das Verhalten an der Wahlurne zusammenhängen. Wir argumentieren, dass online ausgeübte politische Aktivitäten entweder die Wahrscheinlichkeit des Stimmensplittings verringern („Echokammer“-Argument) oder erhöhen („Deliberation“-Argument) können. Empirisch überprüfen wir diese Argumente anhand der Daten der Schweizer Wahlstudie Selects 2019. Die Ergebnisse einer hierarchischen logistischen Regressionsanalyse stützen keines der gegensätzlichen Argumente. Zusätzliche Analysen deuten jedoch darauf hin, dass politisches Interesse die Beziehung zwischen online ausgeübten politischen Aktivitäten und Stimmensplitting moderiert: Wer politisch interessiert und gleichzeitig online aktiv ist, ist eher geneigt, Stimmen zu splitten. Comprendre les conséquences politiques de la numérisation est un défi important pour les sociétés modernes. Une question urgente est de savoir si les activités politiques en ligne rendent les gens moins ouverts à des opinions et arguments politiques divergents. Nous examinons cette question en nous appuyant sur une particularité du système électoral suisse - le panachage, c’est-à-dire la répartition des voix entre plusieurs partis. Nous soutenons que l’activisme politique en ligne peut soit rendre les gens moins enclins à répartir leurs voix (argument de la « chambre d’écho »), soit plus enclins au panachage (argument de la « délibération »). Les résultats d’une analyse statistique basée sur les données de l'étude électorale suisse Selects 2019 ne corroborent aucun des deux arguments. Néanmoins, les analyses suggèrent que l’intérêt politique modère le lien entre l’activité en ligne et le panachage. Within the past years, social media and the Internet more generally have become an increasingly relevant source of political information and an important arena for political activities (Shin & Thorson, 2017). While almost everyone makes use of the Internet for everyday matters on a daily basis, it has also overtaken other media as source for political information (Latzer et al., 2020). Particularly during election campaigns, voters use social media and online platforms to gain information about parties and candidates and to express their own political positions. It is argued that a medium “that provides the public with the information it needs quicker, cheaper, or in a more convenient form is likely […] to change patterns of behavior” (Tolbert & McNeal, 2003: 175). In times of debates about increasing polarization, it is an important question what these behavioral changes induced by the increasing relevance of the Internet and social media look like and whether they strengthen or rather undermine democratic processes. More precisely, how do online activities relate to political attitudes and behavior? Do political online activities lead to echo chambers that create closed political mindsets and ultimately increase opinion polarization? Are online activists no longer open to considering alternative political standpoints, to “hear the other side”? Or do political online activities strengthen deliberation and the openness to alternative political viewpoints? Finally, how does this all play out in political behavior at the ballot box? We address these issues and open questions by studying the link between political online activities and vote splitting in the Swiss national elections 2019. If online activities increased voters’ attitudinal segregation but also the segregation between those who consume news and information online and those who do not, this would be a serious democratic concern (Flaxman et al., 2016). Knowing, processing, and deliberating divergent political views can be considered a core element of liberal democracy (Downs, 1957; Huckfeldt et al., 2004; Mutz, 2006). Accordingly, the question of how citizens build their opinion and in how far their selection of specific, maybe biased, information affects opinion formation, has a long history in electoral research (e.g., Festinger, 1957; Fischer et al., 2005; Zaller, 1992). While the increase in online news was then expected to encourage the creation of echo chambers or filter bubbles, these fears have accentuated with the recent shift towards social media (Allcott & Gentzkow, 2017). On the contrary, there is hope that social media and online platforms will make opposing political arguments more accessible (Garrett et al., 2013; Shaw & Benkler, 2012). This – so the assumption – could support deliberation and overcome political divides. Even though numerous studies have asked whether the use of the Internet and social media has changed citizens’ media diet and opinion formation for the worse or the better, the existing knowledge is still inconclusive (Dubois & Blank, 2018). Against this background, our study goes beyond previous research in four important ways. First, while many articles focus on attitudinal consequences, we study the behavioral consequences at the ballot box. Considering a peculiarity of the Swiss electoral system, we study whether voters who actively engage with politics online are more or less likely to split their votes across different parties. We use this unique factor of the Swiss electoral system (Selb & Lutz, 2015), which can be seen as a maximum variant of preferential voting (Lutz, 2011), as a novel behavioral measure. While a voter may split votes for various reasons, e.g., strategically, because she is undecided between two parties or because she knows and likes specific personalities from different parties, we expect the likelihood of vote splitting to also be related to a voter’s degree of openness towards various political positions and parties. In this vein, a voter wrapped up in his preferred party’s echo chamber will very likely not cast a vote for another party. Conversely, a voter who has been exposed to various arguments and positions is more likely to perceive several parties or at least single candidates from different parties as eligible and, thus, to consider vote splitting. Second, most of the existing evidence stems from the United States and Great Britain. Due to their majoritarian electoral systems, these societies are more prone to polarization. Thus, evidence from Switzerland as the prototype of consensus democracy will indicate to what extent earlier findings on the political consequences of digitalization can be generalized across different political contexts. Third, previous studies have typically focused on specific online platforms like Facebook or Twitter (Bakshy et al., 2015; Barberá et al., 2015; Blank, 2017; Himelboim et al., 2013). These might vary concerning their degree of polarization and the extent to which they contribute to the creation of echo chambers. Moreover, this supply-side perspective neglects that most individuals engage with and receive information from various sources (Dubois & Blank, 2018). Focusing on the online engagement of individual voters independently from specific platforms enables us to receive a more general measurement of political online activities. Lastly, the phenomenon of splitting one’s vote is an under-researched topic in the Swiss case. From a comparative perspective, the issue has been addressed distinguishing between horizontal (i.e., voting for different parties when several equivalent offices are contested) and vertical (i.e., voting for different parties at the, e.g., regional and national level) vote splitting (Burden & Helmke, 2009).1 The Swiss variant of vote splitting among different parties within elections to the same representative body, i.e., the lower chamber of the national parliament, has only been discussed from an institutional and descriptive perspective (Bühlmann et al., 2016; Linder & Mueller, 2017). To the best of our knowledge, no study exists examining the individual determinants of vote splitting (in the Swiss context).2 Hence, we will also present important evidence on the determinants of vote splitting in Switzerland. To assess the link between online activities and vote splitting, we use data from the panel module of the Swiss Election Study Selects 2019. It includes a comprehensive measure of respondents’ online activities (e.g., discussing politics online, sharing and commenting on political information), which enables us to identify political online activists.3 Moreover, the data set includes an individual measure of vote splitting across parties and political camps. This measure will serve as the dependent variable. We thereby assume that vote splitting across parties and political camps is less likely for voters with polarized opinions and a closed mindset. If political online activists and those who do not engage in political online activities were systematically different in their likelihood to split their votes, this could be seen as an indication that online activities strengthen opinion polarization. Our findings do not support this general conclusion. There is no overall relationship between political online activities and vote splitting in Switzerland. Yet, this overall non-finding covers a group-specific pattern driven by voters’ level of political interest. Whereas political online activities relate to a significantly lower likelihood to split votes among voters with a low general interest in politics, among the political interested, online engagement is positively associated with vote splitting. In this section, we present our theoretical considerations arguing that political online activists differ in their likelihood to choose candidates from different party lists (“panaschieren”) compared to voters who do not actively engage with politics online. In the following, we focus on two mechanisms that could explain such a difference: First and related to the literature on preferential voting (see, e.g., Spierings & Jacobs, 2014), the difference in the likelihood of choosing candidates from different party lists could be the result of varying campaign effects for those who engage with political information online. Second, political online activists could behave differently in elections because they are different, namely concerning their political resources and attitudes. This second perspective is particularly relevant because we define political online activists as individuals who actively engage with political information online (“online activists”). Thus, passively consuming political information during the campaign is not sufficient. Rather, we are interested in those individuals that share, post or comment on political content. Therefore, we integrate arguments and findings from the literature on campaign effects with those on online activism. In the following, we elaborate on these arguments. The role of political campaigns on electoral outcomes has been an intensively studied issue in electoral research (Rady & Johnston, 2006; Schmitt-Beck & Farrell, 2002). Campaigns are supposed to influence voters in mainly two ways (Brady et al., 2006; Dermont & Stadelmann-Steffen, 2018; Holbrook & McClurg, 2005): First, a campaign can unfold a persuasive or information effect, i.e., voters receive new information on the candidates or parties, based on which voters form and potentially change their opinion. Second, campaigns can have a mobilizing effect, e.g., by sensitizing voters for the elections and the importance to cast a vote (for their preferred party). We argue that both mechanisms can differ depending on whether or not voters are exposed mainly to online campaigns and engage with political information online during a campaign.4 Against the background of the growing importance of the Internet, the persuasive effect of online communication and information has received increased scholarly (and public) attention over the last decades. In this context, some scholars have warned early on that, in an online context, exposure to news and political information will strongly depend on ideology-based selectivity and, thus, lead to a confirmation bias where citizens only consume information that is congruent with their initial view (Galston, 2003; Sunstein, 2001). Hence, this point of view is related to the expectation that an online environment would strengthen previously identified structural and motivational mechanisms leading to selective exposure and motivated reasoning (Huckfeldt et al., 2004; Taber & Lodge, 2006). Moreover, the spread of social media in recent years may have further increased the relevance of selective exposure and echo chambers. One reason is the way individuals receive and engage with information. While at the beginning of the Internet era, individuals still needed to actively seek information online, in times of social media, information is literally brought to them – and it is strongly pre-selected. Several authors emphasize that news consumption strongly depends on what friends like and share, but also on the content individuals see based on algorithms (Bakshy et al., 2015). In contrast, reading discrepant information means that this content needs to be searched for explicitly, something that only a minority chooses to do (Bakshy et al., 2015). The latter becomes especially unlikely, given that individuals might often not be aware that they are in an echo chamber (Gillani et al., 2018). Furthermore, the social media structure is very different from previous (online) media technologies, mostly because biased content can much more easily spread and, thus, few persons may reach and influence a much broader partisan audience (Allcott & Gentzkow, 2017). While it has been argued that fact-checking online could be an effective tool to reduce such misinformation and to increase political knowledge (Fridkin et al., 2015; Wood & Porter, 2019), in a real-world scenario, this may be of little help, since exposure to fact-checking is likely to be biased as well. Shin and Thorson (2017), in this context, show that “partisan selective sharing” by a small but highly active group of Twitter users has the potential to further polarize the online audience and even reduce individual trust in fact-checking. However, the idea that increasing online information is associated with stronger selective exposure is not uncontested. Some authors point to the opportunities of online environments to foster deliberation. In particular, it is argued that the supply of (diverse) information – both congruent and counter-attitudinal – is just much larger in an online context (Dubois & Blank, 2018: 730), which could facilitate cross-cutting dialog (Shaw & Benkler, 2012), a core element of a well-functioning liberal democracy (Huckfeldt et al., 2004). In any case, according to this strand of literature, the greater choice in online information does not necessarily lead to more selective exposure but, conversely, it could be assumed that exposure to pro- and counter-attitudinal information is positively correlated (Garrett et al., 2013), i.e., is larger in an online context both concerning pro- and counter-attitudinal information. For the US context, Garrett and co-authors (2013) indeed find no evidence that the digital information environment at the beginning of the millennium has led to a “turn towards avoidance”, but rather that those individuals who consume explicit one-sided information also tend to look out for discrepant information. Campaigns can not only influence election outcomes by affecting citizens’ opinion formation, but also by mobilizing voters, i.e., motivating them to actually cast a vote for their preferred party (Holbrook & McClurg, 2005). When it comes to the question of whether and how online mobilization differs from traditional offline activities, one of the most prominent expectations is that the Internet and, more recently, social media offer parties and candidates more personalized and cost-effective ways to engage with voters (Aldrich et al., 2016). However, evidence on the scope and effectiveness of such online mobilization is mixed. Some authors emphasize that personal contact, e.g., door-to-door mobilization, is the “gold standard” to reach and mobilize voters, with online mobilization by parties reaching a smaller audience than traditional offline methods (Aldrich et al., 2016). Conversely, others argue that due to low costs, online mobilization may be broader in scope (Vaccari, 2017). Moreover, the comparative study by Magalhães et al. (2020) suggests that online mobilization is effective, i.e., increases voter turnout (Tolbert & McNeal, 2003). Interestingly, however, the boost effect is greatest in voters who have been mobilized both online and offline. This supports the notion by Vaccari (2017) that online mobilization does not happen in a vacuum. In particular, online mobilization will make less of a difference in a context where citizens are already strongly engaged. While the literature on campaign effects discussed above mainly focuses on individuals who engage online with politics more broadly, in this article we focus on those individuals within this group who assume a more active role. Hence, we also have to consider that these political online activists might just be a different group of people with different participatory resources and potentially even attitudes compared to non-activists. Several studies analyze the determinants of online participation (Anduiza et al., 2010; Best & Krueger, 2005; Feezell, 2016) and mobilization (Krueger, 2006) and find that traditional resources for political participation like education, income, or age are not directly correlated with online participation and mobilization. Yet, these classical determinants of participation are related to political interest, Internet access, and Internet skills, which are in turn strong predictors of online activities. While these findings do not nourish the hope of those who expected that online mobilization could reduce participatory inequalities compared to traditional mobilization activities (Vaccari, 2017), they do suggest that online political activities might require somewhat different skills than offline activities, not least of course because the former are computer-based (Anduiza et al., 2010: 364). Related, another strand of research has focused more strongly on attitudinal attributes that make online engagement more likely. In this vein, Kaye and Johnson (2002) document that political trust, interest in politics, political efficacy, electoral participation but also partisanship are positively related to using the Internet to search for information. Swigger (2013) concludes that online activities and attitudes towards basic democratic values are positively correlated in younger cohorts. While these studies are not conclusive on whether Internet use is the reason for these differential attitudes or rather a “symptom” of sharing according attitudes, they document that voters engaged online are different not only concerning the political information they receive or how they are reached by campaign activities but also related to more fundamental democratic values. What the discussion has shown so far is that voters who engage with political campaigns online and their “offline counterparts” may be affected by varying campaign effects, namely online activists may be exposed to stronger and more homogeneous persuasion for one particular view and with more personalized mobilization. Moreover, they may be involved in more personalized campaign activities by parties and candidates. Furthermore, the two groups may also vary ex-ante, i.e., have different political skills and attitudes that make them more (or less) likely to be active online. However, it is yet another question whether and how these differences actually have electoral consequences, i.e., lead to different electoral preferences and, eventually, behavior. For example, Strandberg (2013) concludes for the Finnish context that social media use in the campaign was low compared to more traditional channels, and its impact on voting even lower. We argue that vote splitting is a suitable phenomenon to investigate the electoral consequences of political online activities. In Switzerland, for the elections to the lower chamber of the national parliament, which is elected based on a proportional electoral rule, voters can adapt their electoral (party) lists in two ways.5 They can choose to cast one or two votes for the same candidate on a list, and they can put candidates from different political parties on their electoral list. The latter can be considered a variant of concurrent, horizontal vote splitting (Burden & Helmke, 2009). We argue that vote splitting can be conceived as a proxy for political open-mindedness because it captures the willingness of voters to split their vote among candidates from different parties. While voters may do so for ideological or candidate-related reasons, in any case, vote splitting demonstrates their willingness to deprive their preferred party of individual votes. We proceed with applying the two mechanisms of online activities elaborated above to formulate hypotheses on the varying likelihood of vote splitting among voters who engage and voters who do not engage in political online activities. First, summarizing the literature on news consumption and engagement with political information in a digital and, most importantly, social media world, there are reasons to believe that persuasion effects are likely to occur when individuals engage in political activities online. The political information individuals receive and consume online can be expected to be more homogeneous and more partisan than information people receive via more traditional news channels like newspapers, TV, or radio. One-sided and congruent information has been shown to have a stronger persuasive impact (Chong & Druckman, 2007; Matthes, 2012). If online activists are more likely to engage with such homogeneous information, this may lead to a stronger conviction that the preferred party’s position is the only “true” one. As a result, they should be less likely to split votes among different parties. Second, we argue that next to persuasion effects, mobilization effects via social media and online platforms might also play a role in the Swiss context. In the Swiss electoral system, mobilization is key in various respects. Parties have to make sure that voters cast their ballots in a first step and that they concentrate their votes on the party’s own candidates in a second step. Additionally, the possibilities to split votes across parties and concentrate votes on single candidates incentivizes candidates to launch personalized campaigns. These personalized features of the Swiss electoral system are important with regard to online mobilization effects. Hitherto, documented evidence for online mobilization effects mainly stems from the United States and Great Britain, which might be related to the majoritarian electoral systems in these countries and the focus on single candidates in according elections (Aldrich et al., 2016). We argue that these effects are also likely to occur in Switzerland because of the personalized features of the electoral system. Candidates have an interest in establishing personal links and/or making themselves visible beyond their party’s general campaign activities to increase their chances to gain some votes beyond their own party base (Selb & Lutz, 2015; Tresch et al., 2020: 53). Using online tools and channels to do so seems particularly attractive since these are much cheaper than traditional offline campaigning (Magalhães et al., 2020; Vaccari, 2017). As a result, we expect online activists to be more strongly mobilized from and for candidates of their preferred party through personalized, visible online activities (“echo chamber”-argument). H1: Political online activists are less likely to split their vote among candidates from different parties. H2: Political online activists are more likely to split their vote among candidates from different parties. Finally, the group differences between people who engage in political online activities and their “analog” counterparts raise the question of whether political attitudes and predispositions might affect the way citizens engage in political activities and for what purpose. Thus, attitudes and predispositions might moderate the relationship between political online engagement and vote splitting. Two different aspects of a person’s political stance need to be distinguished. On the one hand, political interest can be expected to affect the degree to which individuals might enjoy the possibility to engage with different political opinions, i.e., benefit from the “high-choice media environment” (Dubois & Blank, 2018: 731) the Internet offers. Dubois and Blank (2018) indeed show that political interest decreases Internet users’ likelihood to end up in an echo chamber. On the other hand, the ideological position may involve a contrasting mechanism. For party supporters, online activities might mainly serve the purpose of campaigning for their party. Additionally, strong partisans are known to be more likely to engage in motivated reasoning (Bartels, 2000; Mutz, 2007). Citizens with extreme ideologies might have a higher possibility to follow specific sites and blogs that strengthen their preexisting viewpoints. H3a: The likelihood that political online activities are positively related to vote splitting increases with higher levels of political interest. H3b: The likelihood that political online activities are negatively related to vote splitting increases with the extremity of political ideology. H3c: The likelihood that political online activities are negatively related to vote splitting increases with the strength of partisanship. To study the link between political online activities during the election campaign and vote splitting, we use data from the Swiss Election Study Selects 2019. In particular, we make use of the panel module of Selects (2020). Starting in May 2019 (wave 1: 20th May – 8th July 2019), respondents were surveyed three times using an online survey. Wave 2 was fielded during the campaign (wave 2: 2nd September – 17th October 2019) and wave 3 was launched after election day (wave 3: 21st October – 9th December 2019). The panel study aims to observe citizens’ behavior and attitudes during the campaign. Its sample is based on a random sample drawn by the Federal Statistical Office using their sampling frame SRPH. 7’939 online interviews were completed in the first wave which represents a response rate of 31 percent. In the third wave, 5’125 interviews were completed (65 percent of the first wave) (Tresch et al., 2020). In our analysis, we combine data from wave 1 and wave 3, as sociodemographic and basic political variables were included in wave 1, while our core variables were fielded in wave 3. Furthermore, we add macro variables on the cantonal level to the survey data. These include the number of seats in the National Council, i.e., the lower chamber of the national parliament, allocated to the various cantons and the main language spoken in the canton. Since vote splitting, our main dependent variable, is only possible in cantons that vote on at least two seats, we exclude cantons with only one seat from our analysis (Uri, Obwalden, Nidwalden, Glarus, Appenzell Ausserrhoden, and Appenzell Innerrhoden). The deletion of these small cantons and case-wise deletion of observations with missing values leaves us with 2’948 respondents in 20 cantons who are included in our analysis. Our main dependent variable is vote splitting. We measure vote splitting using a dichotomous variable capturing whether respondents have modified the voting list by voting for candidates from different parties. Figure 1 depicts the share of voters who have split their vote across parties per canton. On average, almost every second voter in the 20 cantons split the vote. The cantonal variation implies that a hierarchical model accounting for the nested structure of our data is reasonable (see below) but it also implies that vote splitting is not a mere function of a canton’s size and thus the practical opportunities to split the vote. Vote splitting across the Swiss cantons Note: Dashed vertical line illustrates the overall mean; own calculations based on Selects (2020) We are interested in measuring whether vote splitting is correlated with political online activities that have the potential to make citiz