Usually US politicians scatter around a two-dimensional space (roughly the standard economic/social axes). In those rare times, like now, when everyone lines up along a single axis, there is an instability where one party fractures. #PhysicsOfDemocracy
For federal elections, splitting the GOP into two competing crank Nazi movements would be great for Democrats. At the state/local level, however, we'd be condemning large portions of the South and Midwest to governance by Crossfit George Wallace's.