sane democrats that could be mccain's vp?

[Stranger in a strange land]

Nelson is a conservative, but he's a Democrat. If he didn't switch parties back in early 2005 when the Republican brand was in far better shape, he's sure as heck not going to do so now. I'd assume that to some extent, his views are reflective of those of his constituents, and his being in the majority party likely helps them.

Lieberman is a possibility, but his stump presence is stultifying, he's almost as old as McCain, and his liberal views on social issues would likely put off a great part of the Republican base, causing some to defect to Barr or Baldwin. Plus his views on the war and Iran are pretty extreme.

Mike Bloomberg isn't a democrat, but he might be the type you're thinking of.