This thesis represents the first large-scale analysis of budget reconciliation in decades. Through an American Political Development lens, I argue that budget reconciliation, initially legislated in 1974 to be a tool for crafting budget policy as such, has transformed from a tool for comprehensive, budget-oriented policy-making into a tool for narrow, targeted policy-making in issue areas like tax and health policy, with various implications for public policy. First, reconciliation thus develops its own policy scope, with stable external boundaries but increasingly narrow internal policy-making objectives. Second, while related to polarization and the Senate filibuster, these two factors do not robustly interact with reconciliation to impact legislative output and policy outcomes over the course of reconciliation’s development. Rather, procedural aspects of reconciliation, most notably the Byrd Rule, have exerted significant and sometimes suboptimal policy-design effects on public policy. Finally, across its development, reconciliation has represented a critical tool for conservative economic policies of retrenchment and tax cuts, suggesting institutional party-asymmetry. This research contributes to the APD literature by analyzing an understudied institution through this lens and prepares policymakers for a world in which reconciliation is becoming the primary means of enacting major legislation.