Since the police and the federal administration have allied, and they both have a lot to lose in a democratic election, it is completely conceivable that we will see wide scale arrests, voting center shutdowns, unacceptance of any results, and likely outright violence. The main contender for the presidency has already made public statements about how the military may be necessary to remove this administration from office post election.
Honestly, it just feels like status quo for the parties. With 3 branches of government and a 2 party system, one party usually has 2 of 3 branches. I think it's dangerous for 1 party to have all 3. I just feel like every election cycle it's the end of the world for one of the parties. In fact, I think only Regan and Bush Sr didn't have the party support in congress for part or all of their terms.