Background/Context: Validity issues are often discussed in technical terms, but the context changes when measures enter broad public debate, and a wider range of interests come into play. Purpose: This article, part of a special section of TCR, considers the political dimensions of validity questions as raised by a keynote address and panel discussion originally held at Teachers College in March 2012. Research Design: This is an analytical and reflective piece, based on the author's participation in the panel and drawing on his experience and writing on the broad issue of politics and research. Conclusions: Technical expertise in the construction and interpretation of measurements is important in the new world of high-stakes and "evidence-based" education policy, but the political realities, when measures go public, make the exclusive reliance on such expertise problematic.