Are Redistricting No-Split Rules Neutral? Post-2020 Ohio as a Case Study

The enforcement of city- and county-preserving “no-split” rules in redistricting can complicate estimations of the expected partisan seat splits and responsiveness of neutral map drawing, even creating the impression that these nominally partisan-blind rules favor one party. This work presents a case study of Ohio’s post-2020 Congressional and legislative redistricting to illustrate how a new spatial analysis technique can quantify the (surprisingly small) statewide and localized impacts of these map-drawing constraints on expected outcomes of neutrally drawn maps, consistent with results from a recently published parametric study of seven populous states. The conversion of votes to seats also appears minimally shifted when building districts out of communities of interest rather than administrative boundaries. The lack of a significant no-split effect is attributed to the low fraction of seats that are in the competitive range and thus possibly impacted by applying no-split rules.