Basically you're talking large scale gerrymandering
I can imagine a lot of people getting dreamy about splitting up the country on political lines. Imagine having almost everyone in your country voting for a single party! We could finally sweep that damned inconvenient democracy under the rug of history where it belongs.
Actually, there are already too many places in this country where leaders are decided at the primary level. We don't need to make it worse.
It almost sounds like some people would prefer a civil war or splitting the country up instead of the most likely real-world alternative: Losing the next election cycle in a landslide.
Make that a second landslide.