Giuliani: I Wouldn't Want to Be Biden

"I think Biden must have a sore neck by now," Giuliani said. "He was shaking his head so much it looked like he was on a string. It would be hard to sit there and shake your head all the time."

Biden has also had harsh things to say about Giuliani. During a Democratic presidential debate in 2007, when Biden was a candidate, he said Giuliani is "the most underqualified man since George W. Bush to seek the presidency."

"There's only three things he mentions in a sentence: a noun, a verb and 9/11," Biden said.