Across advanced, consolidated democracies outsider, anti-establishment, and change-oriented demands and action have become commonplace. The prevalence of these demands and actions has led to a growing awareness that politics outside the mainstream matters, but we know very little about the interests, organizations, and participants existing outside the political mainstream in contemporary democracies. What is going on outside mainstream politics and to what effect? This dissertation illuminates what is happening at the borders of democratic politics, offering a novel multi-method, multi-country, multi-organization comparison of non-mainstream interest organization and participation. I begin by outlining my conceptualization of the democratic fringe as a political movement industry occupied by organized actors articulating and acting to advance preferences for political system disruption and expansion. Next, I describe the fringe in an original dataset of more than two hundred fringe organizations in Canada, the United States, and the United Kingdom. Identified organizations represent party movement organizations (PMO) motivated in common by a disruptive drive. As a next step, interviews with PMO participants show that fringe consciousness motivates involvement. Fringe consciousness is identification with fringe, independent, or alternative politics based on personal disaffection with the political status quo and view that politics is in need of a significant change from the outside. Finally, evaluating survey data in the United States, I find that political engagement, particularly through online and protest activism, increases the likelihood of considering fringe participation. Overall, I show that the democratic fringe offers a meaningful space for political engagement and venue for change-oriented interest expression and is an important part of contemporary democratic life.