Northern Ireland's political system is dominated by an Irish Catholic nationalist versus British Protestant unionist faultline, based upon the long-running argument over whether the region should remain part of the United Kingdom or form part of a United Ireland. Yet the largest category of elector in Northern Ireland says they are neither a unionist nor a nationalist and the third most popular political party is now Alliance, which is not aligned to either of the two traditional constitutional positions. Drawing upon a unique in-depth survey of its members, this volume analyses the history and contemporary rise of Alliance and the surge of a centrist party in Northern Irish politics which is challenging the old order. How has a party which eschews ethnic bloc politics, has no constitutional preference, and contains a mix of Catholics, Protestants, and many of no religion come to prominence in a polity whose political institutions are framed upon an old binary divide? The Alliance Party of Northern Ireland undertakes an extensive membership survey analysing the role of a non-ethnic party in an ethnic system, assessing Alliance identities, politics, and futures. Can Alliance integrate Northern Irish society through shared education and housing or will continuing polarisation thwart the Party's project? Would Alliance take a position in the event of a constitutional referendum on Northern Ireland's future - and what might that stand be? These and other key questions form part of a novel study of the party of Northern Ireland's often overlooked centre ground. The volume is essential reading for those wanting to understand how non-ethnic parties can survive and even thrive within an ethnic party system.