To quote myself, "I would say that all those who follow Jesus are given freedom to vote if they choose, but nowhere do I sense that this is an obligation."  So, to stick with your good analogy – if I am sick and want to go to the doctor, I may freely choose to do so.  But, as one who worships the healer of all creation, this might not have to be my default position. 

I'll say it another way, or rather let Paul say it another way, in the context of a discussion about matters of conscience, the apostle Paul says, "… everything that does not come from faith is sin."  (Rom. 14) This is why I did not vote.  Because in my estimation that action, for me, would not have been coming from faith in God – it would have been coming from my faith in non-church politics and a system so compromised that I worry about just how much a role I play in it. 

Laurie, you sound to me like a person who has a stronger conscience in this matter than me and I encourage you in it.  With all sincerity I pray that if God chooses, God will guide me to a place where I can vote and participate in the political realm of the world "in faith," but until that day comes, I feel like I made the most God-honoring decision that I could.