That is another false dichotomy based on your assumption that you can predict the future as well as an assumption that you can read minds.
I won't support Romney but I don't know that he will not still win. And it doesn't matter. The result is irrelevant when I don't want either choice. The only principle I stand on is that I won't support evil and I have not been reticent to voice that and defend it.
The future is not hard to predict. Of course, someone could drop dead, or there could be some cataclysm, but with 99.9% certainty either the republican or democratic nominee will be elected.
And in the end, the only way a candidate wins is by getting more votes than the other candidate. Because of the electoral college, one can easily “not support” or “not vote for” the republican candidate, and it won’t make any bit of difference — for most states, one or the other candidate are guaranteed to win that state.
But that’s not very “prinicpled”, to say “I get to follow my principles because I know there will be no consequences”.
As to your “principle”, I don’t want to put words in your mouth, but in my opinion your principle is really “I won’t support evil, even to stop a greater evil”. You don’t really get to just say “I won’t support evil”, and pretend that this choice doesn’t have consequences.
In World War 2, The United States allied with the evil Russian Empire, in order to stop a more evil German empire. By your principle, we should not have done that, even if it meant Germany took over the world. I’m not deriding your principle, I’m trying to take what you say as truth, and suggest the logical consequence of your argument.