When autocratic ruling parties accede to democratization, they do not always fade away into history. Following forty-one transitions since 1940, including those in Mexico, Taiwan, Bulgaria and Ghana, the ruling party survived and won power after democratization. Why do some former autocratic parties prosper under democracy while others quickly dissolve? What effect does this have on democratic survival? This article uses original data to predict the post-transition fates of eighty-four autocratic ruling parties through 2015. Whereas extant theories emphasize radical reinvention and outsider struggle, the author argues that success is instead about maintaining ruling-party advantages into the democratic period. Parties succeed when they have authoritarian legacies that easily translate to democratic competition, such as broad programmatic experience, strong organization and policy success. In addition, democratic institutions that disadvantage new parties and actors benefit autocratic parties. Lastly, an instrumental variables design shows that autocratic party success negatively impacts democratic survival and quality.