Delaware? New Jersey? Michigan? New Hampshire?
Some of these seem odd; like Romney winning Colorado but losing Tennessee; or Warner winning Ohio but losing Michigan.
Delaware - I think Romney's moderate stance would assist him in Delaware and bring New Jersey extremely close. Likewise New Hampshire. I think he also has a bit of a personal vote there in Michigan because of his father.
Mormons in Colorado and Nevada help him there, but Warner's southern charm and populism help him in Ohio and Tennessee.
That's my thought on it, anyway. I could well be mistaken, but I think Romney would play well in New England (at least for a Republican) and Warner would do less so (for a Democrat). IMO enough to flip Delaware and NH, but not enough to deliver some of those other states.
Romney also does well when talking about the economy, so that would help in Michigan - heck, it might even help with Ohio...
I think Warner would certainly do well in the South (for a Democrat) whereas Romney wouldn't do so well in the south (for a Republican). Again, not enough to flip states like Mississippi, Alabama, maybe bring it close in Georgia, but enough to swing North Carolina, Tennessee, Kentucky, West Virginia, Virginia, Arkansas and Missouri.