I have voted straight Republican every year since my first vote for Reagan in 1980. Except twice, I think.
I left the top of my ballot blank in 2012, and I think I might have in 2008... although I can't be certain. I may have voted for McCain so I could vote for Palin.
It was easy for me; no moral crisis involved. In both cases, my vote would not have mattered in my state, and I knew it.
“I may have voted for McCain so I could vote for Palin.”
I voted for Palin myself. In fact, on my McCain/Palin bumper sticker I took a black marker to it and completely obscured the McCain.