Interest groups are critical actors in American policymaking providing support or opposition to policy changes. This chapter investigates the opportunities that interest group constellations create for policymakers involved in public budgeting. We develop and empirically assess the impact of three interest group environments: capture (stable competition among very few groups over time), instability (variegated competition among a changing set of groups), and deadlock (stable competition among many groups over time). We match interest group data to expenditures for all states. Capture and deadlock environments see steady changes in spending on particular issues, while instable interest group constellations result in volatile budgeting oscillating between short-term gains and losses. Therefore, these patterns of policy changes associated with interest group competition provide different opportunities for policymakers.