The good folks at Democratic Convention Watch have been keeping tallies of the Republican superdelegates (or "automatic delegates") who have pledged for the various candidates. This distribution looks a lot like the others:
scared of possible blowback if they publicly endorse... it's hard to say.
Second, the distribution above again convinces me that Rick Perry remains the only viable alternative if Romney somehow falters. Yes, his public performances have ranged from abysmal to just passable, with the median being closer to abysmal. But he still has the broadest insider support after Romney and would probably be the easiest for the party to rally around.
Update: Another way of looking at the above data: