“…To capture the varying effectiveness of party discipline, the career-related dependence of MPs on their party, compared to other principals (e.g., voters), has been approximated. Empirically, holding or ambitions to reach powerful offices (Kernecker, 2017;Bhattacharya and Papageorgiou, 2019;Zittel and Nyhuis, 2019) strengthen, whereas an MP's need for personal votes in the general election (Sieberer, 2010;Sieberer and Ohmura, 2021) or in intra-party primaries (Sozzi, 2023), personalized campaign styles (Zittel and Nyhuis, 2021), local ties (Tavits, 2009), economic interests of an MP's constituency (Stiller, 2023), outside earnings (Mai, 2022), a low prospect of being promoted to higher office (Benedetto and Hix, 2007), career ambitions at another political level (Meserve et al, 2009), party switching (Gherghina and Chiru, 2014), impending retirement (Mai et al, 2023, but Willumsen andGoetz, 2017 for non-results) or being a 'career politician' (Heuwieser, 2018) weakens an MP's propensity to toe the party line, arguably due to a changed effectiveness of party discipline compared to the baseline MP.…”