This book uses the work of Castle and Fett (2000) and Richard J Fenno (1873) to compare defection in the US political system with crossing the floor by MPs in UK Parliament between 1994-2010, when New Labour were a dominant force. It first explains these authors' suggestion that US Congressmen move for career based reasons rather than political ones, before looking at examples from British history and three case studies from the New Labour era. These case studies are Alan Howarth, Shaun Woodward and Quentin Davies. Based on personal interviews with these three switchers, along with the historical examples, this work argues that British MPs change parties not for career based reasons but largely for ideological ones. In all these cases the MPs themselves have remained relatively consistent whilst the parties changed around them until they were no longer compatible, whilst at the same time New Labour became a much more attractive prospect.