Markovits, ElizabethHouston, SerinHilton, AdamMalpas, Amelia2022-05-162022-05-162022-05-16http://hdl.handle.net/10166/6337Bernie Sanders lost the Democratic presidential nomination—twice. And yet, since his first loss in 2016, the Democratic Party has moved toward his policy stances on a range of issues. Ideas that pundits derided as politically impossible when he first ran are now at the center of the policy debate within the party. Sanders lost his insurgent bids, but the “political revolution” he sought to ignite continues through a movement of progressive insurgents in the House of Representatives like Alexandria Ocasio-Cortez and Nina Turner. Like Sanders, most of these insurgents lose. Despite this, they are a serious force pushing Democrats left. This is puzzling: how do insurgents change political parties and national politics so rapidly when nearly all fail to win election outright? Drawing on original interviews with over 40 insurgent candidates and raw data on campaigns and congressional legislation, this thesis develops a theory of insurgency and insurgent-driven party change, provides a portrait of the Progressive Insurgency, determines what factors predict its candidates’ electoral success, and examines its impact on Democratic Party policy. It finds that the Progressive Insurgency is a semi-coordinated movement that aims to capture the Democratic Party to reorient its policy priorities and through that, turn the United States into a multiracial social democracy. The predictors of insurgents’ vote share vary by type of district—based on the Democratic Party’s institutional and electoral strength—that they run in, but largely concern the quality of the insurgent, like their electoral experience, endorsements, and fundraising. The insurgency has had a substantial influence on Democrats’ policy conversation and proposed policy but only a limited impact in its passed policy. This thesis argues that the efficacy of insurgency comes from its simultaneous institutional and ideological challenge to its host party and that, measured by its rate of electoral victory and policy impact on the Democratic Party, the Progressive Insurgency has been moderately successful. It makes empirical contributions to the study of the Progressive Insurgency, which has yet to receive deep scholarly attention, and theoretical contributions to the study of insurgency and insurgent-driven party change, which remain under- theorized relative to their frequency in American politics.en-USProgressive InsurgencyDemocratic PartyBernie SandersAlexandria Ocasio-CortezParty ChangeThesispublic