I’d have to have a Zell Miller before I’d back any candidate from any party that is pro-abortion, pro-gun control, pro-gay, and pro-secularism.
Your Zell Miller example is an excellent prototype. Reaching a little further back, I’d say Henry “Scoop” Jackson would be another. Here in OK, we have Dan Boren as a Congressman (D) and sits on the NRA board. He is a mixed bag and his daddy, former US Sen. David Boren, was fully in the Obama corner for the 2008 primaries and Convention.