States are unique in the U.S. federal system as both individual governments and entities representing citizen interests. This article explores why certain state coalitions are more effective when filing amicus curiae briefs at the Supreme Court.

The argument centers on coalition representativeness, suggesting that regional diversity matters more than ideology for influencing outcomes. Using a comprehensive dataset of state amicus filings from 1960 to 2013, this study analyzes success rates through logistic regression.

Findings:

* Regional diversity in coalitions significantly increases the likelihood of achieving the preferred outcome.

* Ideological differences among states within a coalition do not impact filing success.

This result contrasts with existing literature on state amicus filings, which often overlooks regional composition as a key factor. The findings offer new insights into how states can strategically form coalitions to shape Supreme Court jurisprudence.