Voter intimidation. If the Dems win it won’t be legitimate.
Lots of voters will go into the booth and vote straight Republican as an “up yours!” to the mobs. Growing violence is going to drive Deplorables/Normals to the polls in a backlash wave, IMO.
Unless Antifas are blocking voting sites with bats and bike locks like the Black Panthers did in 2012. Their impact will be directly related to the politics of the mayor to either deploy the police or order them to stand down.