In the United States, politics has become increasingly nationalized in recent years as voter decision-making is now driven by partisan or national political forces rather than the attributes of individual candidates. Indeed, voters now seem more concerned with which of the two national parties will be in power across all levels of government as opposed to which candidate will represent them individually. The phenomenon has now reached levels unseen since the nineteenth century, when the party ballot was in use and voters were generally unable to select among individual candidates. Nationalized Politics asks and answers the question, "how has nationalization influenced elections across different political eras?" Jamie L. Carson, Joel Sievert, and Ryan D. Williamson look at historical variation in nationalization through an analysis of congressional elections from 1840 to 2020. By examining roughly 180 years of elections, the authors leverage considerable differences in electoral competition, electoral rules, nationalization, polarization, and partisan advantage via the incumbency advantage. Moreover, Carson, Sievert, and Williamson employ a unique survey design to capture citizen attitudes toward the nationalization of politics to further consider the question of how nationalization is currently shaping politics. Providing a comprehensive history of US congressional elections, Nationalized Politics illustrates the roots of the current electoral landscape in the US.