Among other projects, I recently completed a monograph (under contract with University of Chicago Press) on why political parties vary in their ability to adapt to social, economic, and political transformations. Recent decades have shown that political parties differ in their ability to change their strategies and structures in response to a changed environment. This variation in party adaptation is important because the decline of old parties has often made room for radical and populist parties to rise and recently caused widespread concern over the future of liberal democracy. Using the hard test of Christian Democratic parties in Western Europe, this book investigates the sources of parties’ varying levels of adaptation. It is based on extensive archival research in Germany, Italy, and Austria and on additional shadow cases from the same sample of parties as well as France and Japan. Overall, the book explains the varying adaptation of, among others, seven major incumbent parties and covers more than 75 years. It builds on but substantially extends my doctoral dissertation, which won APSA’s 2019 Walter Dean Burnham Award and was Oxford University’s nominee for the PSA’s 2019 Lord Bryce Prize.