I've always felt a little uneasy about voting for the "lesser of two evils" in our country's elections, but it wasn't until I went through a membership class at the RPCNA (Reformed Presbyterian Church of North America) that I finally became fully comfortable with abstaining from voting. The RPCNA has a strong history of political dissent, and while their stance has changed slightly over the years, the RPCNA Testimony still has some interesting things to say about the Christian's responsibilities regarding voting.
Here is a blog post I came across the other day, by Rev. Eshelman of the RPCNA, that quotes the relevant portions of the Testimony. I haven't done any exhaustive study on the topic of the establishment principle (though I intend to, someday, when I get the time), so I reserve the right to change my views in the future, but for the time being, I would say that I am in agreement with the portions of the RPCNA Testimony quoted in this blog post.
A Reformed Voter's Guide
Edited to add: see the comments section for a link to another article with similar conclusions, this one written by an FP.