Hans Noel is the author of Political Ideologies and Political Parties in America (Cambridge University Press, 2013). Noel is an assistant professor of government at Georgetown University. He is also the co-author of The Party Decides: Presidential Nominations Before and After Reform.To most casual observers of politics ideology and party affiliation are synonymous. Noel argues that, while that may largely be the case today, it wasn’t always so. He employs a novel method to trace the articulation of ideology over the 19th and 20th centuries, to explore the way liberalism and conservatism evolved. He writes: “The clear pattern is that in the 19th century, ideology was not unidimensional, but it became increasingly so over the 20th century.”