Actually what you describe is much worse. The racist crackpots take over the party and the conservative centrists sit around and watch their once beloved party turned into a white nationalist orgy. Instead of a disaffected splinter dividing the party, you have the worst elements ruling over the cowardly and the indifferent!
One thing about zombies is they are extremely slow...they can't get to you unless you're surrounded by too many of them. I should tell you about a political conversation I once had in a rural Pennsylvania diner...how I made it out alive I have no idea...at least I don't think I was bitten.