Among criminal justice reformers, it has long been hotly contested whether moderate reform helps or harms more efforts to achieve more thoroughgoing change. With respect to solitary confinement, do partial and ameliorative measures undermine the goal of solitary confinement abolition? Or do reformist campaigns advance—albeit incrementally—that ultimate goal? Call this a debate between “incrementalists” and “maximalists.” I offer this Essay as an appeal for empirical rather than aesthetic inquiry into the question. After summarizing nationwide reform litigation efforts that began in the 1970s, I try to shed some factual light by examining solitary reform efforts in two states, Massachusetts and Indiana. In Massachusetts, early incremental reforms may be providing a blueprint for deeper depopulation of solitary confinement—though the matter is still highly contested. In Indiana, incremental reforms seem to be less effective at achieving deeper depopulation. I offer some hypotheses about the sources of the difference. The evidence suggests that for litigation to trigger broad reform, or significant steps towards solitary abolition, allies are required. In Massachusetts, the political ecosystem has many more reform-minded participants—activists, lawyers, judges, legislators—than does the much redder Indiana. Each such participant can build on the others. In Massachusetts, litigation’s strengths—information generation, thoughtful policy development (codified in settlement documents), publicity, and storytelling—can emerge. Weaknesses—the detachment of litigation from mobilization, hyper-empowerment of lawyers, undue affection for process— are ameliorated by other actors and other actions. The Indiana ecosystem is far less hospitable to solitary confinement change. There is no sign that the limited reformist measures in Massachusetts and Indiana have been perverse, as maximalists might predict. Neither state has seen an increase in the use of solitary confinement or reported worsening of conditions in solitary. In neither state is there any sign that the litigated amelioration of solitary confinement has entrenched or legitimated solitary confinement more broadly.