My research project is a break from the current trend in the literature that focuses on the conflict associated with roll call voting—party polarization and institutional friction. I am interested in determining how policy characteristics of roll call decisions can affect legislators' vote choices. Bills not only differ according to issue content—agricultural policy versus social welfare policy—but also according to how ambiguous they are—a collection of disparate issues versus one specific issue. Using a dataset of House roll calls from 1985-2004 and the Policy Agendas Project content coding scheme, I show that variation in both policy area and policy ambiguity of a given bill is associated with variation in the accuracy of ideology in predicting roll call vote choice. / text