Political justification figures prominently in contemporary political theory, notably in models of deliberative democracy. This article articulates and defends the essential role of partisanship in this process. Four dimensions of justification are examined in detail: the constituency to which political justifications are offered, the circumstances in which they are developed, the ways in which they are made inclusive, and the ways in which they are made persuasive. In each case, the role of partisanship is probed and affirmed. Partisanship, we conclude, is indispensable to the kind of political justification needed to make the exercise of collective authority responsive to normative concerns.