Over the last two decades, as the Supreme Court has sharply cut back its case load, the Solicitor General has wielded the tremendous influence that comes with being the Court’s most frequent and successful litigant in new ways. In this Article, the authors examine both the causes and consequences of these changes, which have diminished the Solicitor General’s role at the certiorari stage and expanded it at the merits stage. They find that at the certiorari stage, when the Court is selecting its cases and setting its agenda, the Solicitor General is now seeking certiorari in so few cases—just fifteen per Term—that the Solicitor General is ceding the federal government’s once-substantial influence over the Court’s agenda-setting to more aggressive litigants. At the merits stage, in contrast, the Solicitor General is now participating in over three-quarters of the Court’s cases, and is doing so more frequently as amicus curiae than as a party. The authors address concerns that, with this nearly pervasive involvement, the Solicitor General may have become too intrusive in private litigation or too partisan in cases presenting high-profile, socially controversial issues. They find, however, that solicitors general have acted within their proper constitutional role, largely confining involvement as amicus to cases that directly and substantially affect the federal government’s institutional interests.