My parents are about as liberal as they come. They have matching Priuses (one red, one blue) with matching license plates that read CONSRV and CNSERV. My father had to see a psychiatrist for months after Bush got reelected (a lot of that had to do with the fact that he works for the US Fish & Wildlife Service with migratory birds that breed on ANWR, so he was directly affected both at work AND everyday life).
Anyway, they've been happily married for 23 years, and trust me, it hasn't been a super easy road. Hell, I caused a lot of problems with my family when I was in high school. The relationship between my father and me went to shit, and my dad really didn't know how to handle raising a teenager. My mom and dad are SO ridiculously different when it comes to understanding the behavior of kids that it really did cause a strain in their marriage for a while (you'd understand if you knew the whole story). Anyway, divorce was NEVER brought up. My parents both worked very very hard to maintain their relationship (along with their sanity), along with the relationship between my father and me. They knew that yeah, there were some serious issues going on, but they truly love and respect the hell out of each other and went through a lot of rough times without considering divorce an option. Things are better now than I think they've ever been, both between my parents themselves and between my parents and me.
If there was ONE thing, and one thing only, that I always respected and admired about my parents, it was their love for one-another and ability to work together, even through the hardest of times, and support one another in any way possible.
Choosing to stay married just to avoid the whole divorce thing isn't necessarily always the best option, particularly when a couple is very unhappy (and I'm not just talking about "oh, we're unhappy at this very moment because we're in a fight").