Philosophically, voting for the lesser evil is still voting for evil, and if I choose not to vote for evil, I haven't given my stamp of approval to anyone. In practice, I have voted for the lesser evil (just to slow things down some), but with the hellbound train pulling into the station, no more.
I see where you’re coming from but I can’t agree with that logic. An old preacher friend of mine once said (and I’m sure he wasn’t the first), “I’d rather be that person who is a 1000 miles away from God and taking that first step towards Him then to be the person 2 inches from Him and taking the first step away from Him.” Apply that to politics.
Everything is contantly moving in one direction or the other. To vote for someone with whom you are agree with 10% over someone with whom you disagree with 100% is stilling moving in the right direction.