What are superdelegates?

NEW YORK (FOX 5 NEWS) - For Bernie Sanders, superdelegates are a source of major frustration. For Hillary Clinton, they are a security blanket and buffer. So what are they?

Superdelegates are -- for the most part -- current and former politicians in the Democratic Party as well as members of the Democratic National Committee and other party leaders. Bill Clinton is one in New York. So is Andrew Cuomo. Even Sanders is a superdelegate in Vermont.

Most of the delegates are pledged. But here's what sets superdelegates apart: they can change their mind if they've already supported a candidate or they can choose to not support a candidate until the actual convention.

In all, New York has 44 superdelegates. Of those 44, nearly all support Hillary Clinton. And that's something the Sanders campaign says it is working on.

Stuart Appelbaum is a superdelegate. He was a Bill Clinton delegate in 1992 and 1996, and now is supporting Hillary Clinton. She said he has received calls from people asking if he would consider switching to Sanders, but he said he hasn't heard a compelling reason to do so.

He doesn't think superdelegates should tip the scales for a particular candidate, but they're helping Clinton rapidly close in on the magic 2,383 total delegates needed to clinch the nomination.

And despite the super name, I'm told they don't have super powers.