Comparative politics scholars argue that consensual democratic institutions encourage power-sharing that promotes ‘kinder, gentler’ politics. We uncover one reason why this is the case: elite inter-party cooperation in consensual systems is associated with reduced inter-party hostility in the mass public. This is because governing parties’ supporters feel much more warmly towards their coalition partner(s) than we can explain based on policy agreement alone. Moreover, these warm affective evaluations linger long after the coalition itself has dissolved. We substantiate our arguments via analyses of CSES survey data from 19 western democracies between 1996-2017, showing that current and past co-governance is associated with substantially warmer inter-party affective evaluations. This implies that electoral systems which encourage coalition governance may defuse partisan hostility.