This study presents a measure of federal constitutional values as a dimension of federal political culture derived from four key features of federal systems. Tested in six federal and two non-federal countries, we find the measure is stable and taps enduring values, including confirmation that citizens who support devolutionary reform have stronger federal constitutional values. Defining federalism success as a system where citizens have strong federal constitutional values and high satisfaction with their current polycentric system, our results find Switzerland and Canada being the most viable, followed by the United States, Australia, and Germany, while Belgium is not very successful. In the non-federal countries, substantial support for devolution and possibly federalism is found in France, but devolution is more contested in the United Kingdom. The results affirm the importance of public attitudes and political culture in understanding the performance of federal political systems and public support for federalist-type reforms.