This dissertation uses the important empirical case of the American climate change debate to ask the following questions: How do governmental experts respond publicly to the politicization of policy issues? What leads to the dominance of technocratic frames in policy domains? How does contention over the meanings of policy issues shape policy domains? The three stand-alone articles provide new evidence for answering these questions. I use an original dataset that I developed specifically for this dissertation and employ quantitative and qualitative text analysis, as well as statistical methodology on longitudinal data derived from a content analysis of congressional testimonies over the span of four decades. The first article examines the behavior of governmental experts in the face of the politicization of climate change and looks beyond the usual arguments about subservience or independence from politics to explain this behavior. The second article tracks the evolution of the climate change debate in the climate policy domain and investigates the reorientation of this debate towards economic reasoning. The third article looks more closely at the discursive dynamics between governmental agencies and politicians to assess the state of this policy domain at different points in time and within different social and political contexts.