How does the balance of partisan control at the national level influence state politics? Unlike decades past, partisan control of the federal government is now virtually up for grabs in every election. As a result, when one side manages to gain unified control of the presidency and Congress, they face strong partisan incentives to actually act on their agenda. This is deeply problematic for those in the minority. Not only do they have little control over the national policymaking process, but their past policy achievements and favored programs are jeopardized by the majority.

Outside of Washington, this political context also has implications for state lawmakers. Unlike national politics, unified control of state governments has reached historic levels, with 38 states under unified government (as of September 2021)---up from a low of 19 states in 1998. Meanwhile, average seat margins in state legislatures have expanded considerably, with veto-proof majorities also reaching all-time highs. As a consequence, majority-party lawmakers are increasingly free to run their states in a way that is consistent with their party’s governing philosophy, with little to no resistance.

In this dissertation, I advance a theory of contemporary state policymaking centered on the idea of out-party threat, in which majority-party lawmakers---guided by electoral considerations---exhibit more partisan policy activism as their state’s policy preferences are increasingly threatened by federal action from the opposing party. As the balance of national partisan control changes, so does this out-party threat, which, in turn, re-calibrates the political calculus for state lawmakers. I test my theory by examining state lawmaking from 2001 to 2019, a period during which the federal government oscillated between unified and divided partisan control. Using data on bill introduction and enactment across twelve of the most common policy areas in state politics, I find that more threatening political contexts lead to higher volumes of bills introduced in states controlled by the national out-party, particularly in policy areas more important to the party's base and in states that are less nationally competitive. Only among Democratic-controlled states, however, does this heightened volume actually translate into more bills enacted into law. These results serve to re-shape our understanding of contemporary state policymaking and federal-state relations, shedding light not only on why states may choose to engage in partisan policy activism, but under which national political conditions.