An earlier version of this article was presented to the Midwest Political Science Association and was awarded the 2006 Harold Gosnell Prize for Excellence in Political Methodology. We would like to thank Steven Abney, Scott Adler, Scott Ainsworth, Frank Baumgartner, Ken Bickers, David Blei, Jake Bowers, Janet Box-Steffensmeier, Patrick Brandt, Barry Burden, Suzie Linn, John Freeman, Ed Hovy, Will Howell, Simon Jackman, Brad Jones, Bryan Jones, Kris Kanthak, Gary King, Glen Krutz, Frances Lee, Bob Luskin, Chris Manning, Andrew Martin, Andrew McCallum, Iain McLean, Nate Monroe, Becky Morton, Stephen Purpura, Phil Schrodt, Gisela Sin, Betsy Sinclair, Michael Ward, John Wilkerson, Dan Wood, Chris Zorn, and seminar participants at UC Davis, Harvard University, the University of Michigan, the University of Pittsburgh, the University of Rochester, Stanford University, the University of Washington, and Washington University in St. Louis for their comments on earlier versions of the article. We would like to give special thanks to Cheryl Monroe for her contributions toward development of the Congressional corpus in specific and our data collection procedures in general. We would also like to thank Jacob Balazer (Michigan) and Tony Fader (Michigan) for research assistance. In addition, Quinn thanks the Center for Advanced Study in the Behavioral Sciences for its hospitality and support. This article is based upon work supported by the National Science Foundation under grants BCS 05-27513 and BCS 07-14688. Any opinions, findings, and conclusions or recommendations expressed in this article are those of the authors and do not necessarily reflect the views of the National Science Foundation. Supplementary materials, including web appendices and a replication archive with data and R package, can be found at http://www.legislativespeech.org.