Political parties are still conceived as key actors for democracy not only for their ability to present candidates to the elections but for their role in the representation chain and their linkage function between civil society and the state (Dalton, Farrell, and McAllister 2011; Lawson 1980; Lawson and Merkl 1988). However, it is widely accepted that the links between political parties, civil society and the state have substantially changed over time, thus changing also the nature of the internal participation within parties (Katz and Mair 1995, 2009). The research strand on party activism has been developed by party politics scholars mainly interested in the drivers of active and passive party members and the main activities members perform. That said, the seminal studies pointed out a long time ago how the dynamics and rationales of party activism might differ substantially from those observed in the study of party membership. For example, declining membership figures might not necessarily lead to less party activism because parties might try to compensate one with the other (Scarrow 2000). Another example is how while the pull of party members has become more of a heterogeneous group, that has not been the case for party activists (see for instance van Haute and Gauja 2015; Heidar 2006).

Most of the comparative literature on party activism has focused on highlighting the sociological and attitudinal differences between active and passive party members. This research strand has built on previous studies on political behaviour and participation. One of the most relevant approaches in the study of party activism is the use of the General Incentives Model (GIM), developed in the early 1990s, to explain party activism. This model mixes several factors such as social norms, resources, altruism or selective incentives to understand forms of high-intensity participation in political parties (e.g. campaigning, attending meetings, becoming candidates) (Seyd and Whiteley 1992; Whiteley et al. 1994; Whiteley and Syed 2002). In this regard, the GIM model took into account explanations based on social resources (status, education, etc.), on the social-psychological literature and the rational choice explanations developed by previous literature on political behaviour (Clark and Wilson 1961; Muller 1979; Muller and Opp 1986; Verba and Nie 1972; Verba, Schlozman, and Brady 1993). The GIM model has been successfully applied to several comparative case studies, often from Anglo-Saxon and Northern European countries (Bale, Webb, and Poletti 2020; Clarke et al. 2004; Demker, Heidar, and Kosiara-Pedersen 2020; Gallagher and Marsh 2002; Seyd and Whiteley 1992; Whiteley and Seyd 1998; Whiteley and Syed 2002). While this is one of the core research strands within party politics, there are still important questions to be answered in the study of party activism. Questions that deserve further attention are those linked to the implications of the different patterns of party activism, the type of activities activists engage in, the presence of multi-speed memberships or the challenges this potential heterogeneity in activism might pose to political parties.

However, the study of party activism in other countries beyond traditional Western democracies -like the cases included in this volumen- may offer some distinctive advantages. While the existence of different patterns of membership across Europe has been documented, less attention has been paid to the particularities of party activism in Southern Europe. Firstly, many of these countries do not always follow the same evolution as their other Western counterparts. Mair and van Biezen’s article (2001) already found that countries from Southern Europe like Spain or Greece followed an opposite pattern with increasing figures, in contrast with the general path of party membership decline (Mair and van Biezen 2001, 12). More recent studies still observe this increasing trend in Southern European countries like Spain, Italy or France (Biezen and Poguntke 2014, 208). Secondly, Southern European countries have seen recently successful challenger parties making their breakthrough in national legislatures, enlarging the structure of opportunities for party activism. Podemos or 5 Stelle have been able to achieve fast affiliation by offering new forms of involvement (Barberà et al. 2021; Biancalana and Vittori 2021), while Ciudadanos or Vox have seen raising important figures of paying-fee members in a very narrow span of time. Finally, these countries have particularly been affected by the Great Recession and its social effects, which have triggered movements of social protest against governments and ruling parties.

From a research design perspective, the study of party activism using quantitative approaches has slowly evolved from the study of party elites. In this respect, the main reference for truly comparative analysis of intraparty activism in these countries still lies in the ‘European Political Parties Middle-Level Elites’ (EMMPLE) research project, which inspired several generations of researchers in different countries to survey party congress delegates (Niedermayer 1986; Pierre 1986; Reif, Cayrol, and Niedermayer 1980; Reif, Niedermayer, and Schmitt 1986). Despite its limitations, the EMMPLE project served as a starting point in the study of the sociology and activities of party delegates that has continued for decades (Baras et al. 2015; Boy et al. 2003; Espírito Santo, Lisi and Ferreira 2018; Ignazi and Bordandini 2018; Sandri, Seddone, and Bulli 2015). More recently, the project ‘Members and Activists of Political Parties’ has contributed to the renewal of party membership and party activism research across European countries surveying party members online (Demker, Heidar, and Kosiara-Pedersen 2020; Gomez et al. 2019; Lisi and Do Espírito Santo 2017). Similar research strategies have opted to survey participants (members and followers) in party primaries instead of party members (Bernardi, Sandri, and Seddone 2017; Seddone and Sandri 2020). However, in contrast with the trend in other European countries, party activism has also been analysed from a more qualitative approach in Southern Europe. Concretely, in France, a relevant research avenue to understand party members activities and the nature of party activism in Southern European countries came from successive revisions of the ethnographic method and in-depth case studies (Bachelot 2012; Faucher 2021; Kriegel 1970).

The study of party activism in Southern Europe has substantially improved over the last decades, reducing knowledge gaps with other Western regions such as Northern Europe or countries such as the United Kingdom. The widespread use of new technologies such as online surveys and better training in quantitative methods has substantially contributed to doing so. There are still some remaining differences, though. First, the analysis of party activism in Southern Europe tends to be country-oriented or based on small n designs. As we previously stated, several monographs are dealing with party activism at a country or subnational level, but a general analysis at a regional scale is missing. Further collaboration between academics from different countries is needed to have a better understanding of such phenomenon. Second, in Southern Europe, the research faces some hurdles that do not seem to be the case in other countries: access to political parties, party activists’ willingness to participate, funding to conduct comparative research, and so on. Third, so far the use of survey data from large comparative projects such as the World’s Value Survey or the European Social Survey has not been explored in detail and the participation of these countries in these comparative projects has not been consistent. While this kind of research is emerging as a plausible strategy to avoid the comparison difficulties of the country focused analysis, it is not very predominant yet (Ponce and Scarrow 2014; Whiteley 2011).

Aiming to fill this gap, the studies included in this volume analyse different aspects of internal participation using different approaches and methods. The article by Antonella Seddone, Fulvio Venturino and Giulia Sandri compares the patterns of participation of two different sets of party members (enrolled members and sympathisers) in the leadership primaries held in the Italian Partito Democratico between 2009 and 2019. Besides, Patricia Correa, Juan Rodríguez-Teruel and Oscar Barberà focus on Spanish party conventions’ delegates to cluster different sets of activists, according to the nature of the activities developed within their organizations. Adopting a more qualitative approach, Carole Bachelot’s analysis provides a critical review of the French ethnographic literature on internal party activism. Additionally, Javier Alarcón and José Real-Dato change their focus to the activists in youth political sections in Spain, looking for the peculiarities of young party activists. Finally, Rodríguez-Teruel, Correa and Barberà conduct a comparative analysis of party activism across European countries to test the impact of the Great Recession on party involvement.

As these contributions show, there is not one single way to study party activism. Indeed, multiple methodological strategies can be adopted. Most of the research on party activism tends to implement quantitative approaches (van Haute and Gauja 2015; Ponce and Scarrow 2014; Whiteley and Syed 2002), building on survey data either from party surveys or from general population surveys, as the contributions on Spain and Italy in this volume show. Nonetheless, French scholars have tended to adopt often a qualitative approach based on case studies and the use of ethnographic research. The use of quantitative approaches helps us to provide a general understanding of the trends of activism and the core explanatory factors, building on individual and aggregated data. Alternatively, as Bachelot reflects in her article, ethnographic studies allow us to account for quality or informal aspects of activism such as the socialization effects or their informal practices. This provides a better understanding of the general organizational cultures of parties and their activism cultures in particular.

Beyond the methodological approach, the studies in this special issue can be grouped by the following general themes: who is active and what type of activists are they, why they are active and what are the main differences in activism across different individuals, parties or countries. Starting with identifying those individuals active in the party, the comparative study by Rodríguez-Teruel et al. shows how individuals living in a country most affected by the Great Recession have been more active in particular periods than those living in countries that did not have to recur to a bailout. Beyond the country in which you live, individual factors such as sociodemographic factors are still relevant to predict party activism. Nonetheless, their relevance differs depending on the type of activities or the intensity of activism. As such, Alarcón and Real-Dato show males, members over 18 and members involved in other associations are more involved in any type of party activism. In contrast, their results indicate those with higher education are more involved in more demanding activities, while this matters less to explain involvement in less demanding activities such as monetary contributions to the party, also named ‘economic activism’. Correa et al. show the existence of four different types of party activists in Spanish parties. These four types vary not only in the general intensity of their activism but also in the type of activities they are involved in. The authors show how some sociodemographic factors matter to assess who is active and what type of activist they are. Their results indicate women are more likely to be a mass party, a committed or a canvasser activist in comparison to being a cheering activist and members with higher levels of education are less likely to be activists from the most demanding types: the mass or the committed activists. Interestingly, while individual resources seem to matter to predict young party member activism aligning with previous literature, the results are more inconclusive when trying to understand different patterns of activism within political parties. An important takeaway point from the two contributions on Spain is the need to undertake more nuanced research on party activism. Beyond the general aggregate level of involvement, studies need to consider the type of activities members engage in and the potential existence of different profiles of activists in line with the results of previous Northern European studies (Demker, Heidar, and Kosiara-Pedersen 2020; Heidar 1994). On the other hand, when comparing members and non-members, Seddone et al. illustrate how party members and sympathizers follow a similar trend regarding participation in party primaries, although their voting choices differ in some contexts.

Moving on to the other explanatory factors of activism, the contributions to this special issue have shown how contextual factors such as the access to a bailout during the Great Recession, the levels of government effectiveness or the levels of regulatory quality matter to understand a general country level of activism. Studies at the party level indicate how the particular organizational culture and the type of interactions among party members are important to understand different logics and dynamics of activism as Bachelot reflects on. For instance, the article suggests ethnographic studies can help understand better the personal relations among members and how they might influence the way members engage in the party. The two contributions on Spain, one analysing young party organizations and the other on general party organizations show a relationship between demographic and socioeconomic factors and party activism in line with studies on political participation (Verba, Schlozman, and Brady 1995). Additionally, both articles support previous research highlighting individual incentives are important to understand not only the likelihood of being active but also the type of activism (Clark and Wilson 1961; Whiteley et al. 1994). Interestingly, Alarcón and Real-Dato show that outcome incentives are important to explain party activism while process incentives reduce the likelihood of engaging in economic activism. Similarly, Correa et al. results also indicate material and solidary incentives are important for party activism. This is the case, especially, to explain activism requiring a more demanding involvement and commitment from members. While the Italian article is based on aggregated data and follows a more exploratory approach, their results suggest that different types of attachment to the party matter to understand the levels of competitiveness in party leadership selection. Overall, insights from Spain and Italy highlight the relevance of accounting for the heterogeneity within party activism when researching political parties nowadays.

While we find many commonalities among the articles included in this special issue focusing on Southern European countries, some discrepancies across countries and different levels of party affiliation emerge that are worth mentioning. First, the comparative article shows how Spain and Portugal follow a similar trend in the evolution of activism, but this is not the case for other European countries. For instance, in Greece, all types of party affiliation (grassroots, militants or supporters) have decreased in numbers. In France, the grassroots have increased while in Portugal and Spain are militants and supporters the ones that have increased. Second, the comparison between young members and different types of activists in Spain showed how not only the relevance but also the direction of the effect of some common indicators explaining party activism varies when we adopt more nuanced definitions of activism. Finally, each article has focused on different explanatory variables, combining individual-level, party-level and country-level factors, and highlighting, in turn, the complexity of the phenomenon we are analysing. This suggests the need of using different prisms to provide a more comprehensive explanation of party activism in Southern Europe and beyond.

While these articles help to fill some gaps in the comparative literature on party activism, they also point out some weaknesses in our current knowledge about the topic. In this respect, there are some challenges to address in future research. First, we need to strengthen our empirical understanding of party activism with a separated perspective from general party membership. In the context of the raising multi-speed party membership, party activists are not just those members with high-intensity participation, but a distinctive strand of party affiliation, where formal enrolment might become less important than in the past. Secondly, as party membership and party activism figures seem to remain more stable than in the past, we should pay attention to more dynamic explanations that may account for ups and downs in the short term. Hence, electoral success and failure, the development of intra-party democracy tools, and the contextual political and social evolution may be as important as structural features of party models to understand how the function of linkage is fulfilled over time. Finally, these avenues also need a stronger combination of quantitative and qualitative approaches in the research on party activism, which may help to bring agency decisions into the equation. Overall, the studies included in this volume suggest that party activism is far from a declining reality. As previous recent studies have also suggested, political parties are facing new opportunities to respond to new social demands of representation, and new modes of party activism are pushing in that direction.