For decades, political scientists have had two divergent views on lobbyists in Washington. On the one hand they focus on the privileged access of a few groups in balkanized issue niches, and on the other they observe highly inclusive lobbying campaigns where hundreds of lobbyists vigorously compete for policymakers’ attention. Not surprisingly, these disparate observations lead to contradictory conclusions about lobbying tactics, relations with relevant policymakers and the nature of interest group influence. In this article, we make a simple, yet novel, empirical observation: these seemingly incongruent observations of lobbying at the micro level are not inconsistent when we uncover the structure of lobbyists’ interactions at the macro level. That is, both views are correct, depending on the policy context. Using data from 248 543 Lobbying Disclosure Act reports filed between 1998 and 2008 – which consists of 1 557 526 observations of 32 700 individual lobbyists reporting activity in 78 issue areas – we reveal that the Washington lobbying community has a fundamental and stable core–periphery structure. We then document how the empirically derived core–periphery mapping is a superior way to differentiate bandwagon or niche policy domains. As transaction cost theory suggests, we find that policy domains in the core have more in-house lobbyists and more revolving door lobbyists. And, on average, lobbyists active in core domains represent a greater diversity of interests and tend to be policy generalists. The converse is also true. Highly specialized contract lobbyists drift toward those sparsely populated domains in the periphery where they may focus on obscure policy minutiae, relatively free from public scrutiny. Our findings have important implications for the study of lobbying and interest representation. In Washington, there are really two worlds of lobbying. The first world, where most lobbying attention is directed, is one in which we see a great deal of interconnectedness and interest diversity. The second world, home to an overwhelming majority of policy domains, cultivates niche lobbying and policy balkanization. That these two worlds exist simultaneously is precisely why observers fail to agree on what ‘typical’ or ‘average’ lobbying is. We believe that this is why the political science literature on interest groups have been contradictory for so long. The abstract core–periphery structure we uncover also has important practical implications for influence in Washington. At first glance, those highly competitive policy domains in the core appear to embody the pluralistic ideal. However, we show that these conditions give interest groups the incentive to hire revolving door lobbyists, who sell access to former employers – not highly specialized expertise – at a premium. Existing lobbying disclosure and revolving door regulations do little to level the playing field. Washington’s most powerful interests know they need to staff up with large numbers of former government officials if they want to stick out in the crowd. Indeed, it appears to be one of the most effective ways to find a seat at the center of the conversation.