The Core of the Party System

We propose tests of core and Condorcet winner (CW) status of parties and of core/CW existence and implement them using preference data on 1,176 parties from 196 election surveys. Applying strong control of the family-wise error rate, the fraction of core parties is 26.5% (and as high as 48.1%), and the core is not empty in all surveys at the α=0.05 level of significance. Similarly, a CW exists in 13.8% (and as many as 42.3%) of surveys. In the subsample of nonpresidential democracies with minority parliaments, we estimate that core parties participate in government (respectively, control Prime Minister office) at a higher rate by 23.8 (13.8) percentage points and CW parties by 37.3 (46.9) percentage points. These estimates imply that these democracies overwhelmingly meet a classic normative criterion for party-based representation. We uncover and empirically document mechanisms that contribute to core parties’ success.