Someone who always votes for incumbent Senators who aren't being seriously challenged, regardless of party. I don't really get this mindset, but it appears to exist to a large degree.
I've done it. While Senate elections are no less "political" than House ones, I see the role of a Senator as to serve as a kind of senior spokesperson (perhaps that's why the minimum age for a US Senator is 30, vs. 25 for Representative). Thus, I voted to re-elect Sen. Carl Levin (D-MI) in 2002, even though I was closer to his GOP opponent on some issues and most of the rest of my ballot was Republican; I valued Levin's experience, especially after 9/11.
