The last century witnessed a staggering rise in the number of interest groups active in American politics. While this fact is well known, we lack a comprehensive study of the number of groups, the identity of groups, the timing of their births, their mobilization decisions, and their tactical choices, beginning before the transformation and continuing to the present day. In this paper, we use Supreme Court nominations to conduct precisely such an analysis. Analyzing new data on the 52 nominations from 1930 to 2017, we document a sea change in interest group politics. Prior to the 1970s, nomination politics were characterized by a small number of active groups, infrequent opportunistic mobilization, and somewhat restrained inside-oriented tactics. The 1970s saw a surge in both liberal and conservative groups, while the 1980s saw a continuing surge, largely on the conservative side. Moreover, the types of groups shifted from labor unions, core civil rights groups, and "old right" groups, to public interest, ideological, and identity politics groups. By the late 1980s, nomination politics was characterized by a large number of groups, routine ideologically driven mobilization, and extremely vigorous outside-oriented tactics. In sum, the data show a transformation from relatively genteel pluralism to street-fighting hyper-pluralism.