Here in Polk County, we have seats that have no opposition. Just repukes on the ballot. I voted straight Democratic ticket. Where there were no Dems, I voted for either Green Party or libertarian. I've never voted for a repuke, but I believe libertarians are repukes that like drugs so they can get some sex.
I went office by office because Pete Olson (r) is so popular down here that a LaRouchie was the one who beat him on the dem side (Kesha Rogers) and I will not vote for someone who spends her time hanging up Obama posters made to look like Hitler, and talking about colonizing Mars. Seriously. So, I picked Green for Rep-22. Then I went down the same way and picked D, G, or L for the rest. There were only a couple of repug unopposed - folks like the clerk that does the vehicle registrations - can't mess that up too much.