This paper discusses a new group of parties that we term anti-establishment reform parties (AERPs), which combine moderate social and economic policies with anti-establishment appeals and a desire to change the way politics is conducted. We analyse the electoral breakthroughs of AERPs in central and eastern Europe (CEE), the region where AERPs have so far been most successful. Examples include the Simeon II National Movement, Movement for the European Development of Bulgaria (GERB) (Bulgaria), Res Publica (Estonia), New Era (Latvia), TOP09 and Public Affairs (Czech Republic) and Positive Slovenia. We examine the conditions under which such parties broke through in nine CEE states in 1997–2012 using fuzzy-set qualitative comparative analysis (fsQCA). We find five sufficient causal paths combining high or rising corruption, rising unemployment and party system instability. Rising corruption plays a key role in most pathways but, unexpectedly, AERP breakthroughs are more closely associated with economic good times than bad.