The rise of the Christian Right and the pro-life movement over the last fifty years has transformed US politics in general, and the Republican Party in particular. Its seemingly all-pervasive influence on contemporary US politics has commanded much social scientific attention. (1)However, policy debates over embryonic stem cell research during the Presidency of George W. Bush exposed deep, moral fissures amongst American conservatives. As one of the most recent ‘hot button’ issues in America's culture wars, embryonic stem cell research appeared to energize the under-studied moderate wing of the ‘Grand Old Party’ (GOP), which belatedly emerged to challenge what often seems like a homogeneous and monolithic Christian Right. This paper argues that during the 109th United States Congress, moderate Republicans identified in embryonic stem cells a powerful entity around which to mobilise themselves as a set of otherwise diverse interests. This enabled them to imagine a political future for themselves in which they could successfully challenge the hegemony of the Christian Right in grassroots Republican Party politics. In states like Missouri, however, which fought a referendum on embryonic stem cell research in the 2006 midterm elections, it could be argued that emboldened GOP moderates overplayed their hand. Furthermore, a fully-formed GOP moderate counter-movement to the Christian Right failed to materialize as centrists and moderates were amongst the first to lose their seats when the Democrats reclaimed Congress at the 2006 midterms.