Objectives. Until recently, the signing statement—a written statement the president can append to a bill after he signs it into law—remained buried in the footnotes of history. However, for modern presidents, the signing statement has become one important, albeit understudied, example of presidential unilateralism—strategies employed to preserve executive prerogatives and advance presidential policy in the face of gridlock. This article examines how presidents exert influence through signing statements and their role in the context of the separation of powers.

Methods. Descriptive time-series data and logit models assess signing statement behavior from Ronald Reagan to George W. Bush (1981–2008).

Results. The analysis demonstrates how features of the political (especially unified government) and policy context explain variation in the type of signing statement.

Conclusion. The evidence suggests presidents have incentives to use constitutional signing statements when Congress is the least likely to challenge them and not necessarily for reasons related to policy gridlock.