Comparativists are increasingly researching national border regions. Yet the distinct way in which proximity to borders independently shapes politics is rarely theorized explicitly. Drawing on the emerging subdiscipline of border studies, we identify three types of border effects: Borders involve specific actors, shape local identities, and provide distinct strategies, each of which directly affects key areas of comparative politics. An in-depth review of work on political violence and state formation shows that specifying these effects ( a ) demands that comparativists consider the ways in which borderlands differ from other regions and be careful in attributing processes found there to nations as a whole, ( b ) improves theories by elucidating scope conditions, and ( c ) scrutinizes the validity of our research designs and measurement strategies. We end with a call to move from a comparative politics in border regions to a comparative politics of border regions that contextualizes how borders alter political processes.