WATCH: CNN's Erin Burnett humiliates Rudy Giuliani's son as he tries to attack FBI investigation of his dad

On CNN Thursday evening, Rudy Giuliani's son Andrew went on "Erin Burnett OutFront" to defend his father and slam the federal investigation into his Ukraine work as a political hit job — only to crash and burn spectacularly on national television.

"The thing is, though, to get the warrant, it takes a lot," said Burnett.

"Who signed the warrant? A judge. Who appointed the judge? Barack Obama," said Giuliani. "Since Eric Holder became attorney general, we have seen the Justice Department get politicized ... no other judge would sign this warrant."

"You have any proof no other judge would sign the warrant?" asked Burnett.

"I don't have proof, but do you have any proof that any other judge would sign the warrant?" demanded Giuliani.

After a long detour in which the younger Giuliani tried to steer the conversation to conspiracy theories about Hunter Biden, Burnett cornered him again on his baseless allegations the investigation is politically motivated.

"Let me ask you something important about your claims of political motivation," said Burnett. "President Biden was asked about it today." She played the clip of Biden saying he had no advance knowledge of the raid on the elder Giuliani's home and office. "Do you have any reason to not take him at his word, Andrew? ... I'll just make the point again that his son's under investigation and he's done nothing to stop it."

"So you don't think he actually has the motive to intervene in that investigation?" insisted Giuliani.

"He may, but he hasn't done it," shot back Burnett.

Watch below: