Objective We address whether intraparty democracy conditions political parties’ responsiveness to rival parties’ policy shifts. Method We estimate parameters of a spatial econometric model of parties’ policy positions in 11 established democracies. Results Internally democratic parties respond to shifts in rival parties’ policies, and internally undemocratic parties do not respond to rival parties’ policy shifts. Conclusion We argue that this occurs because intraparty deliberation provides a channel through which rival parties influence their competitors’ policies. Because rank‐and‐file party members are influenced by deliberative processes more than party leaders—and the policy goals of internally democratic parties’ policies are heavily influenced by their party members—deliberative processes lead democratic parties to respond to shifts in rival parties’ policy positions. This work has important implications for our understanding of parties’ election strategies, intraparty politics, and how policies diffuse between parties competing in the same election.