The first mystery guest on The Late Show’s wheel of news Thursday night was Democratic candidate Bernie Sanders. Host Stephen Colbert put Sanders in the hot seat and grilled him on asking Hillary Clinton’s superdelegates to switch.

“You say you are trailing in delegates behind Secretary Clinton and that superdelegates will switch from Ms. Clinton to you as you start winning more states. Why do you want the Democratic party to be thrown into the kind of chaos we’ve seen on the Republican side where they will have a contested convention?” Colbert asked Sanders.

The Vermont senator explained: “Well, we have won six of seven of the last caucuses—most of them by a landslide—and I think the superdelegates should listen to the will of their people. If you get sixty, seventy, eighty percent of the vote in a state, I think superdelegates should vote for us.”

“Isn’t the purpose of the superdelegates so that the party takes some control of the process? Don’t the Republicans just wish they had superdelegates right now?” Colbert asked.

Sanders laughed. “Maybe, but I think what we need in the Democratic party is some democracy,” he answered. “And when we are defeating Donald Trump in the last polls by 15 or 20 points, and when we are the strongest in taking on any Republican candidate, I would hope that superdelegates take a look at who the strongest Democratic candidate is, and that’s me.”

Watch: Bernie Sanders explains the superdelegate mystery: