In 1994, Massachusetts passed legislation restricting localities from enacting rent control. California followed suit in 1995. This paper examines the struggle over rent control in these two states. It begins with an overview of key concepts from the literature in political science, sociology, and public policy, focusing on the major institutional, political, and ideological factors necessary to analyze the mobilization of resources for and against public policy. This is followed by a brief history of rent control in the United States, focusing on the role of political mobilization by tenants, landlords, and their respective allies. A history of rent control and a description of the recent politics of deregulation in Massachusetts and California reveals the political calculations of tenants, landlords, and allies in these two states. The next section of the paper analyzes the major factors involved in the real estate industry's successful campaign to defeat or weaken rent regulations at the state level in these two states. It focuses on the various strategies used by the real estate industry and the tenants' organizations, the mobilization of "third parties," the role of the media and public opinion, and other factors. The final section reviews the consequences of deregulation in these two states. It is reasonable to argue that rent deregulation had already taken effect in California and Massachusetts by the late l970s and early 1980s. The major cities in both states had already adopted vacancy decontrol policies (or no rent regulations at all). A key observation, therefore, is that the overall number of units subject to decontrol, compared with the private rental housing inventory in those metro housing markets and statewide, is quite insignificant. (This is in contrast to New York City, for example, where regulated units comprise a significant proportion of the city's and metro area's private rental housing inventory). Within the particular localities, however, deregulation will certainly increase hardship. The paper uses several kinds of data to indicate the possible short-term and long term consequences. But because the laws in both states were designed to be gradually phased-in, it is impossible to make definitive statements about their consequences, either for sitting tenants or for the availability of affordable housing.