This isnwhat actually is going to happen sometime in the next 2 decades with candidates are going to declare they won and the country is going to balkanize over it.
And I really don't think it'll be a civil war because there's no defined fronts, it'd be all the cities being blockaded by all the surrounding rural areas.
The only thing that might prevent this from happening is if liberals say the republican president won with their compelling argument of "fuck you what're you gonna fo about it" to move forward ad a nation and begin healing.