"They've got a lot of youth, they've got a lot of energy, they've got some significant diversity and they're no dummies," Clinton told Tapper in front of a small audience at a Clinton Global Initiative America meeting in Denver.

"And they believe what they believe," he said in a backhanded compliment. "They still believe trickle-down economics works better than investment, and their convictions are so great that they're undeterred by evidence and that's always amazing to me."

"But they're impressive," he added.

Clinton suggested that the crowded field might pose a real problem for Republicans going forward, particularly in the debates, but he said in the primaries Republican voters will "wind up voting for the person they think has the best chance to win."

The former president also joked about the GOP candidates' concerted efforts to take down Hillary. "They'll all sing in the choir about how bad Hillary was," he said amid laughs from the audience, adding, "And it will be difficult for those who thought she was great when she was a secretary of state and went on record saying it."

Having praised the Republicans for their youth and energy, Clinton also suggested that inexperience and being a Washington "outsider" could end up being an obstacle for potential candidates.

"But that's what makes it for an outsider that doesn't understand all the ins and outs of it," he sad. "It will make it difficult to predict because I think they don't know, do they need somebody who is new? Do they need somebody who is seasoned? Do they need somebody who has got a forward leaning position on immigration, or will it disillusion their people and stay home? They got all these decisions to make. But in the end it's going to come down to who is the most electable candidate because they want to win."

Video via Newsmax.