Defining ‘party family’

Mair and Mudde's (Reference Mair and Mudde1998) seminal piece systematized the attributes traditionally taken into consideration in classifying party families: parties’ names, historical origins, transnational links, and ideology. Already then, though, not all of them seemed convincing for a minimal definition of a party family (Gerring and Collier, Reference Gerring, Collier, Gerring and Collier2009). Rather, ‘all serious attempts at defining or classifying parties take into account the centrality of ideology’ (Ennser, Reference Ennser2012: 155).

The role of ‘ideology’ is thus a shared starting point in the literature. Ennser (Reference Ennser2012: 152), for instance, refers to the ‘concept of party family’ as implying ‘a certain degree of shared political viewpoints among party family members.’ The importance of common ideology is also shared by others (Jungar and Jupskås, Reference Jungar and Jupskås2014: 231), although rarely through explicit definitions and/or with reference to specific ideological dimensions (Kitschelt, 2018).Footnote ¹ Langsæther's (Reference Langsæther2023: 9) recent book spells out a much-needed explicit definition of party family as ‘a group of political parties that share a set of core ideological features,’ although it lacks an indication of specifically which core ideological features should be shared (instead, later explored in the book on a case-by-case basis).

Additionally, the ideology of party families should also be evaluated in comparative terms. Langsæther (Reference Langsæther2023) adds that parties belong within a party family if they are more ideologically similar amongst each other rather than to formations from other party families. Relatedly, Freire and Tsatsanis (Reference Freire and Tsatsanis2015: 3) conceptualized party families based on the fundamental criteria of ideological distinctiveness and cohesiveness: ‘parties belonging to one party family should be significantly distinct from parties belonging to other families,’ and ‘there should be enough ideological-policy cohesion among the parties belonging to each party family.’ These criteria are frequently used in empirical assessments of party families and are surely helpful.

Of itself, though, ideology cannot suffice. Mair and Mudde (Reference Mair and Mudde1998: 220) first thought of the combination between ideology and cleavage or, more generally, historical originsFootnote ² as the conceptual standard: ‘Ideology and origin may also be usefully linked together in a parallel strategy aimed at analyzing the continued relevance and coherence of the whole notion of party families.’ Accordingly, others have referred to this useful linkage in their own definitions of party family, such as Elff's (Reference Elff2013: 8): ‘If a party can be traced back to one of the great ideological currents of the 19th and early 20th century and/or if its party constitution and electoral platforms contain ideas derived from these currents as central elements, then it can be grouped into the appropriate party family.’

Overall, as shown, existing scholarly attempts at grasping the elusive conceptual nature of party family have gone a long way in identifying some of its most central attributes. These foundational elements, however, emerge from conceptualisations of party family that, when explicit, are often formulated in rather general terms. I argue that this is because of the level of abstraction (Sartori, Reference Sartori1970) at which they engage the concept of ideology. On the one hand, ideology is party families’ distinguishing, unique, and historically-rooted quality; on the other, in Mair and Mudde's (Reference Mair and Mudde1998: 220) words, it is yet ‘difficult to define and specify with any precision.’ In fact, if approached in more general and abstract terms – e.g., through left-right heuristics (Bobbio, Reference Bobbio1997) or broad issue dimensions (Bornschier, Reference Bornschier2010) – ‘ideology’ complicates the analysis of party families. This is because the broader the conception of ideology, the more difficult the identification of the ideological features that set individual party families apart.

Operational and empirical complications

The subsequent aggregate-level operationalization of ideology complicates the empirical assessment of canonical party families if this is based on their presumed ideological distinctiveness and cohesiveness. Indeed, these criteria are difficult to gauge at the aggregate level, since this collates several issues—which can be either conceptually relevant or irrelevant to specific party families.

This emerges clearly from existing empirical evidence in the party family literature. Many have analyzed expert survey data from sources such as the Chapel Hill Expert Survey (CHES) (Jolly et al, Reference Jolly, Bakker, Hooghe, Marks, Polk, Rovny, Steenbergen and Vachudova2022). Close (Reference Close, Close and van Haute2019: 336–337) finds widespread ideological overlaps in positioning along the economic and cultural dimensions between several party families, which are a byproduct of both their mean positions (distinctiveness) and varying dispersion of their internal positional distributions (cohesiveness), as descriptively visualized via boxplots. More generally, Langsæther (Reference Langsæther2023: 228) shows that canonical party families can be divided into two broad clusters along the economic and cultural dimensions: a center-left and center-right cluster, with liberal parties oscillating between the latter on the economy and the former on cultural issues. Gunderson's (Reference Gunderson2024) model-based clustering shows a widespread lack of distinctiveness for most center-right party families and cohesiveness for center-left party families, despite breaking down “ideology” into four dimensions (economic, cultural, European Union, and decentralization). Ennser's (Reference Ennser2012: 162) analysis comes to comparable conclusions even when employing different expert survey data, from Benoit and Laver (Reference Benoit and Laver2007): center-right parties such as liberals, radical right parties (RRP), and conservatives/Christian democrats (grouped together) show considerable degrees of ideological heterogeneity. Furthermore, positional overlaps between party families are not uncommon (e.g., center-right families on the ‘taxes vs. spending’ and ‘social policy’ subdimensions, or even social democrats and RRPs on decentralization).

The picture is similar when employing Manifesto Project (MARPOR) data (Lehmann et al, Reference Lehmann, Franzmann, Al-Gaddooa, Burst, Ivanusch, Regel, Riethmüller, Volkens, Weßels and Zehnter2024). Camia and Caramani (Reference Camia and Caramani2012) descriptively show that the ‘ideological left-right’ positions of canonical party families in Western Europe, as measured by MARPOR's multidimensional ‘RILE’ index (Zulianello, Reference Zulianello2014), highlight recurrent cases of limited distinctiveness over time (1940s–2000s). Elff's (Reference Elff2013: 19) comparative-longitudinal analysis of party families’ Bayesian posterior mean positions confirms such findings. On the ‘economy’, ‘libertarianism vs. ‘authoritarianism’, and ‘permissiveness vs. traditionalism’ dimensions, the frequent positional overlaps between party families again stem from the combination of both their mean positions and the dispersion of their internal distributions.

Finally, the illustrated findings on canonical party families’ lack of aggregate-level ideological distinctiveness and cohesiveness also extend to other data sources. This is evident in Freire and Tsatsanis’s (2013: 13–14) analysis of elite data from the Comparative Candidate Survey, in which the ideological features of party families are assessed based on prospective MPs’ issue orientations, reduced to a socioeconomic and a libertarian-authoritarian dimension via principal component analysis.

My argument is that these empirical assessments fail to capture individual party families’ ideological distinctiveness and cohesiveness because of the level of analysis at which ‘ideology’ is operationalized, rather than other conceptual issues. Simply put, by being so broad, the presented measurements of ideological distinctiveness and cohesiveness at the aggregate level capture ideological features that are not part of individual party families’ historically rooted ideological uniqueness. Because, as shown, they systematically introduce noise in doing so, such aggregate-level measurements constitute unduly hard tests of party families’ ideological distinctiveness and cohesiveness. Such empirical and operational issues, in turn, derive from the aforementioned conceptualisations of party family (Adcock and Collier, Reference Adcock and Collier2001: 531): namely, their excessively broad understanding of ideology.

In fact, alternative approaches might be more beneficial, as already pointed out in the literature.

Ennser's analysis (Reference Ennser2012: 161–162) shows that party families tend to display rather cohesive and distinct positions on the specific issues that are traditionally at their ideological core. Langsæther (Reference Langsæther2023: 230–231) also illustrates that specific party families emerge as distinct and cohesive in terms of positions and salience on those issues they traditionally own (Petrocik, Reference Petrocik1996) (e.g., the Greens on the environment; RRPs on immigration). These intuitions should now be systematized.

The issue-level approach

Moving from these premises, my contribution to the literature lies in suggesting an alternative approach to the concept of party family. The generalized consensus is that party families should be distinguished – theoretically and empirically – by their unique and historically rooted ideological features. Yet, as shown, the identification of such an ideological proprium is complicated by the aggregate-level conception of ideology, both conceptually and empirically.

I reckon that, in most cases, party family scholars do not actually have a broad conception of ideology in mind when thinking of a given party family, but rather specific issues — or specific bundles of issues — that they would historically expect that party family to focus on. These are what I call the core issues of a specific party family. How are they, and hence the related expectations, defined for specific party families? This is traditionally based on the cleavage/historical origins of each party family, which are the reasons why specific parties emerge and mobilize politically in the first place.

Further, I argue that, ultimately, it is parties’ salience (Gunderson, Reference Gunderson2024) on such core issues that truly sets party families apart ideologically, making them distinct and cohesive. Indeed, multiple parties can share the same positions on a variety of issues, but the different centrality of core issues will be conveyed by the attention that formations from a specific party family will devote to them; i.e., they will be the parties most distinctively and cohesively emphasizing such issues within a party system.

Therefore, as a conceptual contribution, I hereby propose an explicit definition that systematizes this alternative way of thinking about party family:

This proposed issue-level conceptualisation has the advantage of greater precision in generating specific case-wise hypotheses for the empirical assessment of party families, by better leveraging the potential of the vast knowledge generated on each canonical party family. To this end, Table 1 summarizes specific party families’ core issues based on their cleavage or otherwise more general historical origins, as per seminal works.

Table 1. Canonical party families’ origins and core issues

From left to right, both the varied radical left (RLP) party family (e.g., March, Reference March2011) and social democrats (e.g., Keman, Reference Keman2017) share their origins in the class cleavage and opposite ends of the early-20th-century communist–socialist split. These have subsequently influenced the respective core issues: for RLPs, the rejection of neoliberal capitalism, both through radical left-wing economic stances and opposing the ‘Atlanticist’ international order; for social democracy, the pursuit of greater equality – material and/or of opportunity (Giddens, Reference Giddens1998) – within the accepted frame of capitalism, through redistribution and the welfare state. Further, the Green party family – originating in ‘new politics’ and the emergence of postmaterialist values in increasingly affluent post-WW2 Western European societies (Müller-Rommel, Reference Müller-Rommel1998) – primarily emphasizes issues pertaining to environmental sustainability and climate change. This does not mean that Green parties will not also emphasize other issues, but that they will generally emerge in the respective party systems as the most consistent emphasizers of environmental issues.

The liberal party family – traditionally the most ideologically elusive and heterogeneous party family – ultimately originates from the application of 19th and 20th-century liberalism across multiple cleavages (e,g, Close and van Haute, Reference Close and van Haute2019). Therefore, their core issues pertain to freedom, both in terms of free-market economics and individual rights.

The ideological proprium of Christian democracy is a peculiar and historically rooted bundle of core issues. Christian democrats originate, since the second half of the 19th century, from the Church-State cleavage, the Church's support, and the political application of Catholic social doctrine. Hence, their core issues are a combination of, on the one hand, religious values and morality socioculturally; and, on the other, ‘social capitalism’, centered on family-oriented and earnings-related (rather than redistributive) welfare measures (e.g., van Kersbergen, Reference van Kersbergen1995). Similar reasoning applies to Conservative parties, chiefly—but not solely (Caramani, Reference Caramani2015: 43)—originating from the capital pole of the class cleavage. Indeed, their ideological proprium is the specific combination of core issues deriving from the defense of the existing social status quo both, primarily, in the economy (i.e., orthodox free-market economics) and, after that, in sociocultural terms (i.e., traditional morality and norms) (e.g., Bale and Rovira Kaltwasser, Reference Bale and Rovira Kaltwasser2021). Finally, the varied RRPs, historically originating from fascist formations (Ignazi, Reference Ignazi1992) or more recently by mobilizing ‘losers of globalization’ in the integration–demarcation conflict (Kriesi et al, Reference Kriesi, Grande, Lachat, Dolezal, Bornschier and Frey2008), have nativist and authoritarian issues such as a tough stance on immigration and nationalism/sovereignism at their core – more so than moral traditionalism (Langsæther, Reference Langsæther2023) or economic issues (Mudde, Reference Mudde2007).

Linking the suggested definition of party family and the historically rooted delineation of core issues can provide party family scholars with clearer expectations in the empirical assessment of individual party families’ ideological distinctiveness and cohesiveness. The specific form these probes should take is an open question for future works. On paper, these could take the form of between-issue, within-party rankings or within-issue, between-party rankings. The two serve different analytical purposes and can provide important information as to whether party families distinctively and cohesively emphasize their core issues. Within-party rankings could inform about specific parties’ issue priorities and corroborate the centrality of expected core issues. Of course, they would be sensitive to period effects regarding what issues become more politically salient at a given time, but this issue could be mitigated (e.g., by weighing for issue salience at the party level). On the other hand, within-issue rankings – more sheltered from such dynamics – could show whether there is a correspondence between top issue emphasizers and expected party families based on their core issues, although with less information on the rank of salient issues for individual parties. Regardless, both strategies could be easily implemented – in both descriptive and explanatory analyses – with issue-level data on party supply,Footnote ³ which is ever more necessary at times of increasing political complexity (Hooghe and Marks, Reference Hooghe and Marks2018; De Sio and Lachat, Reference De Sio and Lachat2020; Off and Trastulli, Reference Off and Trastulliforthcoming).

Naturally, this approach comes with limitations. An obvious one, as mentioned earlier, is current data scarcity, especially from a substantively broad and comparative-longitudinal perspective. Other objections are more conceptual in nature. For instance, it is unclear whether periods of profound ideological transformation – e.g., the ‘Third Way’ for selected social democratic parties (Giddens, Reference Giddens1998) – substantively alter the composition of party families. Such reservations, however, are common across all conceptualisations of party family that, to any extent, rely on ideology.

The goal of this note was to provide interested scholars with a potential alternative way to think about party families: one that could, by moving the analysis of ideology to the issue level, provide greater conceptual and empirical clarity, mitigating some of the existing limitations in the literature – lack of explicit definitions, inconclusive empirics – whilst building on existing elaborations – i.e., on the ideology-origins linkage and the criteria of ideological distinctiveness and cohesiveness. As such, this attempt is not meant to replace existing approaches to ‘party family’ but rather to spur further reflection on this analytical tool. It comes with numerous potential empirical applications – such as assessing the empirical fit of canonical party families, recasting parties into party families, or reclassifying party families—and I thus hope to see it further developed in the future on the basis of this initial contribution.