WATCH: Donald Trump claims not to "know enough" about the KKK to distance himself from David Duke endorsement

During an interview in which Donald Trump boasted about his business prowess, threatened Republicans who dared to oppose him, and slagged his former competition for the nomination -- in other words, behaved as per expectation -- he also claimed not to know enough about white supremacy or the Ku Klux Klan to be able to disavow the endorsement of white supremacist and former KKK Grand Wizard David Duke.

It was a remarkable display that left State of the Union host Jake Tapper almost speechless. Tapper began by quoting Duke, who said last week that voting for anyone other than Trump would be "treason to your heritage."

"Will you unequivocally condemn David Duke and say that you don't want his vote, or that of other white supremacists?" he asked.

"You have to understand," Trump replied, "I don't even know David Duke. I don't know what you're talking about with 'white supremacy' or 'white supremacists.' I don't know, I don't know -- did he endorse me? What's going on?"

The apparently confused Trump reiterated that he "know[s] nothing about David Duke, nothing about white supremacists, so you're asking me a question about people I know nothing about."

"Even if you don't know about these groups or their endorsements," Tapper replied, "can't you just say, unequivocally, that you condemn them and don't want their support?"

"I'd have to look at the group," Trump said, "I don't know what group you're talking about. You wouldn't want me to condemn a group I know nothing about! If you'd send me a list of the groups, I'd look at it and would disavow them if I think they [are] doing something wrong."

"The Ku Klux Klan?" a flummoxed Tapper replied.

"There are probably groups in there that are really fine," Trump said, "and it'd be really unfair."

"I'm just talking about David Duke and the Ku Klux Klan," Tapper replied.

"Honestly, I don't know David Duke," Trump said, conveniently eliding the difference between personally knowing Duke -- which he most likely doesn't -- and knowing about him and the KKK.

Watch the entire interview below via CNN.