Can't stand-- hate to me there is a level of intolerance there, no matter what. McCain could not stand and hated Romney. There was no doubt about that.
I have a feeling McCain admires Obama on some level-- especially his being so young, including Obama's discipline and his intelligence.
McCain is old enough to be Obama's father, and their could be some resentment that this is McCain's last chance and he's got a youthful and formidible opponent who could beat him.