Curating Amicus Coalitions
The Advocate–Amicus Ecosystem of the Supreme Court’s Argued Docket, OT2022–OT2025
Amicus briefs are a routine feature of Supreme Court merits litigation. What is less often examined is whether they matter, how they organize around particular advocates, and what the resulting ecosystem reveals about coalition structure across cases and terms.
This analysis uses SCOTUSblog and the Supreme Court dockets for argued merits cases from OT2022 through the October oral argument sitting in OT2025, counting each amicus organization once per consolidated merits matter per advocate. It asks three related questions: does having more amicus support correlate with winning; which advocates draw the broadest organizational backing; and how do those advocate–amicus relationships cluster into a network? The framing draws on Larsen and Devins’s account of the organized infrastructure behind amicus practice and on Solimine’s analysis of how pervasive that infrastructure has become across the argued docket.
A note on methodology. Each amicus organization is counted once per consolidated merits matter—treating sequentially-argued dockets in the same underlying dispute as a single unit—to prevent inflation from related multi-docket litigation. All figures are distinct-organization counts unless noted otherwise.
Does Amicus Advantage Predict Winning?
Before examining who draws amicus support and how it organizes, the threshold question is whether amicus support correlates with case outcomes at all. The short answer, for this OT2022–OT2024 merits sample, is: yes—but the signal is specific to high-volume cases, not large imbalances alone.
Volume, Not Just Imbalance, Is the Meaningful Cut
The amicus-advantaged side—whichever side has more briefs in a given case—wins at different rates depending on total case volume.
Win rates by total amicus volume (sample of cases with clearly defined winners)
Total briefs ≥ 21: advantaged-side win rate 81.2% (32 cases; 95% CI 64.7–91.1%)
Total briefs < 21: advantaged-side win rate 59.1% (115 cases; 95% CI 50.0–67.7%)
The 22-percentage-point gap between high-volume and lower-volume cases is statistically meaningful in this sample. In amicus-saturated cases—those with 21 or more briefs total—the side that attracts more organizational support wins more than four times out of five. In lower-volume cases, the advantage narrows to something closer to a modest baseline tilt.
Large Imbalances Trend in the Expected Direction, But Inconclusively
A separate cut examines whether having a large numerical advantage specifically—rather than simply being in a high-volume case—predicts winning:
Win rates by amicus differential
Absolute differential ≥ 11 briefs: advantaged-side win rate 72.7% (22 cases; 95% CI 51.8–86.8%)
Absolute differential < 11 briefs: advantaged-side win rate 62.4% (125 cases; 95% CI 53.7–70.4%)
Two-proportion test: p = 0.352 (not statistically distinguishable in this sample)
The direction is consistent—larger imbalances correlate with higher win rates for the advantaged side—but the difference is not statistically distinguishable with OT2022–OT2024 data alone. Part of the reason is structural: large imbalances tend to occur precisely in the high-volume cases where the 21+ signal is already doing most of the work. In the 11+ differential group, the median total brief count is 33; in the 41+ total-brief group, the median imbalance is 18. The two phenomena are largely co-occurring.