Analysis of conflict in state politics based on intrastate regionalism is an important, yet neglected, perspective in current scholarship. We demonstrate regionalism’s analytic power by illustrating the case of Idaho. Understanding how regionalism interacts with political culture and political ideology in Idaho should aid the understanding of how the Mountain West (containing the five fastest growing states in the United States in the 1990s) is going to evolve in the coming century. Our research is based on analysis of aggregate data collected at the county level, including a survey conducted in the autumn of 2000 of county-elected officials. We find that regionalism as commonly understood in Idaho needs revision. The north region is really two sub-regions, one extremely conservative, the other the least conservative in the state. We suggest this change in Idaho regionalism affects attitudes toward important policies.