I was in exactly that situation in 2010 in the Toronto civil election. I knew 100% that the candidates other than Rob Ford were terrible.  I knew Ford personally, had met him a few times. I mean, I really KNEW him. I knew exactly what he was (except for the drug thing). And I voted for him anyway. But at least it didn't give him access to nuclear launch codes, or the power to appoint judges. I despise Hillary, but if I was in a swing state I would have voted for her anyway.