From looking at their delegate numbers, Hillary Clinton appears to be way ahead of Bernie Sanders. But that’s counting the superdelegates, a strange class of delegates who are free to change their votes up until the day of the Democratic National Convention.

So while Clinton has way more delegates on her scorecard right now, a lot of those could potentially switch to Sanders. And that’s not an impossibility—Clinton was way ahead in the delegate count in the 2008 Democratic primaries, until many of her superdelegates flipped their votes to Barack Obama.

In the meantime, an inflated lead for Clinton could mean less incentive for Sanders supporters to come out and vote. Which is why the Sanders team gets especially annoyed when Clinton and media outlets count her superdelegates before they hatch.