“…As illustrated in Figure 1, we suggest that routinization can occur via the creation of practices that become regularized over time, whether or not they are codified (regularization), or through adoption and modification of formal rules, such as party statutes (formalization). The concept of regularization reflects arguments in previous studies of PI that the extensiveness of parties’ formally codified organizations is not necessarily synonymous with their levels of institutionalization, because parties’ informal practices and extra-party linkages are at least as important (Bolleyer and Ruth-Lovell, 2019; Levitsky, 1998; Randall and Svåsand, 2002). In contrast, formalization reflects other arguments that have linked routinization to more formal rules, be it the density of rules governing a party’s relations with its followers (Bolleyer and Ruth, 2018: p. 289), or the reification described by Harmel et al (2018).…”