IntroductIonW hat is the nature of the relationship between mass mobilization and democratic change? the question has grown in importance as the elitist leanings of recent decades have yielded to a renewed emphasis on popular contributions to democratization. 1 if it remains the case that "regime changes occur when elites give in, one way or another," 2 then it is increasingly recognized that we need to pursue more fully the sources of elite vulnerability. this has generally been understood in terms of pressure from below: elites will make democratic concessions when faced with substantial, even revolutionary, popular challenges to power and privilege. 3 But do we fully understand how, and how well, this causal relationship works?Britain stands as the ideal type of democratization by elite concession. Within this broader case, the first Reform act of 1832 represents the best case for the thesis that elites yielded democratic gains as a response to the threat of revolution. 4 faced with significant social un-* the author wishes to thank frieda fuchs, samuel Clark, Robert Young, Richard vernon, laura stephenson, Jennifer Mori, Joanna innes, neville thompson and the British history seminar of the University of Western ontario, Carol nackenoff and the Research Colloquium of the swarthmore College Department of political science, the anonymous reviewers of World politics, and especially peter hall for providing critical feedback and helpful advice on this article, as well as anton spadar for diligent research assistance.1 Rueschemeyer, stephens, and stephens 1992; . in the second and third Reform acts, enhanced popular activity emerged in response to elite initiation (Biagini 1992) and perhaps also as a "delayed response" to much earlier Chartist agitation (Rueschemeyer, stephens, and stephens 1992, 96).