A lot of people have been getting exercised over this possibility lately, but I just don't see it happening. The superdelegates are by and large politicians. As such, they have finely-calibrated ears for what will and won't infuriate voters. And there's only one thing they could do to very obviously incur the wrath of voters over the next six months: Anoint a presidential nominee who hadn't won a majority of pledged delegates.
Now, I'm sure there are a handful of ward-heeler types out there who relish the prospect of deciding the party's fate amongst themselves. But, for the most part, I think that mindset died off about a generation ago. And, in fact, if you listen to the superdelegates themselves, it's pretty clear that they don't relish the prospect. Take these fairly typical quotes from today's Adam Nagourney/Carl Hulse piece in the Times:
“Once the primary season is over, I am hoping we will have a nominee,” said Senator Benjamin L. Cardin of Maryland. “If those of us who are uncommitted can help bring that about, then I think we should try to do that.”
Senator Amy Klobuchar of Minnesota, who is neutral, said she would not stay on the sidelines for long once the voting was over. “I will not go through the summer, I can tell you that, without endorsing a candidate,” she said. “I am not a big believer in smoke-filled rooms.”
Having said that, I think it would be generally better if, as Tad Devine recommends today, the superdelegates stood down till the voters had their say. That would make the nominating process less messy and bitter. But, in the end, I don't see someone getting the nomination without a lead in pledged delegates (I think enough superdelegates would reverse their choices to prevent it from happening.) At least as long as the final count is not so close it could plausibly be called a tie (say, under five delegates, with the other candidate winning the popular vote). And if it is that close, then it wouldn't be a question of superdelegates thwarting the will of the people. It'll be a question of finding some workable tie-breaker, which is a completely different proposition, and which you'd expect the superdelegates to play a role in.