Tuesday is the New York Primary. There are 291 Democratic delegates up for grabs. Vermont Senator Bernie Sanders is coming off a streak of wins, but he may have lost the Democratic nomination for president weeks ago. That's because the superdelegates have given most of their votes to former First Lady Hillary Clinton. But what is a superdelegate?

In our occasional explainer series, “Break It Down,” we explore how superdelegates work. We then revisit our conversation with Georgia State University political science professor Sean Richey who weighs the pros and cons of this electoral system.