The advocacy coalition framework (ACF) pays special attention to ‘‘so-called'' policy brokers when explaining policy change. However, this prominent policy approach neither clearly defines who the policy brokers are nor identifies under which institutional rules they have an influence on policy processes and outputs. This article thus formulates two theoretical hypotheses that complement the ACF and then proceeds to undertake the first empirical testing of these hypotheses within the Swiss climate policy (1990–2008). The empirical results show that, in the case under investigation, the strategic interest-based behavior of two policy brokers (i.e., one public administration and one political party), as well as two institutionalized veto points (i.e., optional referendum and parliamentary committee), are crucial factors explaining policy brokers' influence on policy process and change.